Buying or refinancing a home
Compare a 30-year vs 15-year mortgage, see exactly how much a 1% rate cut saves over the life of the loan, find your break-even on a refinance, and budget for closing costs before you sign anything.
Find free online calculators for personal finance, dates and time, health estimates, school math, unit conversions, and home improvement projects.
About this site
The Handy Calculators is a small, independent site with one job: give you the exact number you came for, then explain how it was calculated so you can trust it.
Every tool on this site is hand-built around a real decision — a mortgage you're weighing, a paycheck you're negotiating, a training plan you're starting, a deadline you're counting down to. The formulas come from primary sources: IRS publications for take-home pay, the Mifflin-St Jeor equation for calories, Fannie Mae and Freddie Mac amortization conventions for mortgages, ASHRAE and building-code references for home projects, and peer-reviewed research for the health estimators. When a calculator uses an assumption you can override — a tax bracket, a discount rate, a maintenance reserve — you'll see the assumption spelled out, not buried.
Nothing here is auto-generated fluff. Each page is written and reviewed by a human, tested against worked examples, and updated when the underlying rates, brackets, or standards change. There are no popups, no email walls, no dark-pattern upsells, and the site runs entirely in your browser — none of your inputs leave your device.
Formulas cite IRS, Fannie Mae, ASHRAE, ACSM, and peer-reviewed research — not other calculator sites.
Every tool is checked against at least one manually-worked example before it ships, and re-tested when rates change.
Calculations run entirely in your browser. No accounts, no data collection on inputs, no results sent anywhere.
Real-life scenarios
TheHandyCalculators.com isn't a math reference — it's a decision toolkit. Every calculator is designed around a real situation people face at home, at work, at school, or on the move. Here are a few of the moments our tools were built for.
Compare a 30-year vs 15-year mortgage, see exactly how much a 1% rate cut saves over the life of the loan, find your break-even on a refinance, and budget for closing costs before you sign anything.
Translate a salary offer into real take-home pay by state, compare an hourly contract to a salaried role, and stress-test whether a relocation makes sense after taxes, cost of living, and benefits.
Find your daily calorie target with Mifflin-St Jeor TDEE, dial in a sustainable deficit, track BMI and body-fat trends, and build a training plan around heart-rate zones and realistic running pace.
Calculate your current GPA, weight every assignment by syllabus category, and find the exact score you need on the final to lock in the grade you want — without guessing or scrolling through Reddit threads.
Run cap rate, cash-on-cash, DSCR, and full multifamily, hotel, retail, office, or industrial proformas in seconds — the same math brokers and analysts use, without an Excel template or a paid platform.
Count business days until a deadline, line up meetings across time zones with full DST handling, convert recipes from cups to grams, or estimate concrete, paint, and tile before a weekend renovation.
Why people keep coming back
We obsess over two things: the accuracy of the underlying formulas and how quickly you can get a useful number out of them. Everything else — sign-ups, paywalls, dark patterns — gets cut.
Every calculation runs locally the moment you type — no loading spinners, no server round-trips, no waiting. Most pages give you an answer in under a second on a phone over 4G.
We use the same formulas trusted by clinicians, lenders, and analysts — Mifflin-St Jeor for TDEE, fully amortizing loan math, NOI / cap-rate for real estate, IRS-aligned tax tables, and unit conversions to international standards.
Numbers you type — salary, weight, loan balance, health metrics — are processed in your browser and never sent to a server. There's no account, no tracking pixel tied to your answers, and no email gate.
Available in English, Spanish, Portuguese, and German, with metric and US units side by side, mobile-first layouts, and copy-friendly results that paste cleanly into email, Slack, or a spreadsheet.
FAQ
If you're new here, these are the answers most visitors want before they trust a calculator with a real decision.
Quick links to every tool on the site.
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Use the category links to jump directly to related calculators, then open any tool for instant calculations and clear results. Each calculator is organized by topic so search engines and visitors can discover the most relevant pages faster.
Plan everyday financial decisions with mortgage, loan, paycheck, tax, tip, discount, savings, retirement, and investment calculators.
Monthly payment, taxes, insurance, and required income.
Monthly savings, break-even point, and lifetime savings from refinancing.
Compare the true 5-year cost of renting versus buying.
Monthly car payment including tax, trade-in, and down payment.
Monthly payment and total interest for any personal or auto loan.
How much to save monthly to hit any goal by a target date.
Project your investment growth over years or decades.
Project your retirement balance with employer match and growth.
Total return, profit, and annualized CAGR for any investment.
Estimate take-home pay after federal, state, and FICA taxes.
Add sales tax, GST, HST, or VAT to any price and see the final total.
Calculate tips and split the bill between any number of people.
Find the sale price after any percentage discount.
What a dollar from any year is worth today — adjust for the inflation rate.
Compare snowball vs avalanche payoff — time, interest, and which finishes first.
How many months of expenses you should hold — and how long to get there.
Certificate of deposit maturity value, interest, and after-tax return.
How long it takes — and how much interest you'll pay — at your current monthly payment.
Add up assets, subtract liabilities, see your total net worth.
Convert hourly wage to annual salary (and back) with custom hours per week.
Estimate 1099 SE tax, federal and state income tax, and quarterly payments.
Home equity line of credit: max borrow, interest-only payment, and full repayment cost.
Convert between APR and APY for any compounding frequency.
Live exchange rates between major world currencies — updated daily (ECB).
Salary you need in another city to maintain the same standard of living.
Standard wedding budget breakdown across venue, catering, photo, attire, flowers, music, and more.
Project tax-free Roth IRA growth to retirement and compare it against a taxable account.
Full loan amortization schedule with yearly interest, principal, balance, and extra-payment savings.
Student loan payment, total interest, payoff time, daily interest, and extra-payment savings.
Estimate capital gains tax on stocks or property with basis, holding period, recapture, and state tax.
Annual and biweekly net pay after federal, FICA, and state income tax — all 50 states plus DC.
Profit margin, markup, and revenue from any combination of cost, selling price, and target margin.
Count days, calculate exact ages, add work hours, plan sleep cycles, and compare time zones for deadlines, travel, and schedules.
Countdown to any future date — birthdays, holidays, deadlines.
Your exact age in years, months, days, hours, and minutes.
Add up hours worked between start and end times, minus breaks.
Convert any date and time between time zones — DST aware.
Today's moon phase, illumination percent, and the next full moon, new moon, and quarter moons.
How many lunar months, full moons, and new moons between any two dates.
Days, weeks, months, and years between any two dates — with optional business-days-only count.
Add or subtract days, weeks, months, years, or business days from any date.
What date is 30, 60, or 90 days from today? Calendar days or business days, with day of the week.
Drift-free stopwatch with laps and a countdown timer with audible alert — millisecond accuracy.
Count business days between two dates or add/subtract working days from any date, with custom holidays excluded.
How long it's been since any date — years, months, days, hours, minutes, and live-ticking seconds. Birthdays, quit dates, milestones.
Enter the day your relationship started and see exactly how long you've been together — to the second. Perfect for anniversaries.
Enter your wedding date and see your exact marriage length in years, months, days, hours, and seconds — with traditional anniversary gifts.
Estimate wellness numbers including BMI, calories, hydration, sleep timing, pregnancy due dates, and running pace.
Body mass index in metric or US units, with category.
Keep your waist under half your height — the simple cardiometabolic risk screen.
Models the body as an ellipse from waist and height — predicts mortality risk better than BMI.
Daily calories to lose, maintain, or gain weight using Mifflin-St Jeor.
How many ounces, cups, or liters you should drink each day.
Best bedtime or wake time based on 90-minute sleep cycles.
Estimate your due date and current week of pregnancy.
Pace per mile/km and average speed from time and distance.
Turn your step count into calories burned using MET values, body weight, stride length, and pace.
Convert your daily step count to miles and kilometers — see both at once.
Daily protein, carbs, and fat targets for cutting, maintenance, or bulking based on your TDEE.
Basal metabolic rate using Mifflin-St Jeor and Harris-Benedict, with activity-multiplier TDEE.
Estimate body fat percent with the US Navy circumference method, plus a BMI-based check.
Estimate your 1RM from a working set using Epley, Brzycki, Lombardi, O'Conner, and Lander formulas.
Estimate ideal body weight from height, sex, and frame using Hamwi, Devine, Robinson, and Miller formulas, plus the healthy-BMI range.
Calculate your five training heart-rate zones from age and resting HR using Tanaka, Fox, Gulati, or Karvonen heart-rate-reserve formulas.
Estimated ovulation date, six-day fertile window, and next expected period from your last menstrual period and cycle length.
Convert your dog's age to human years using the AVMA size-aware method or the 2019 epigenetic clock, with small/medium/large/giant adjustments.
Daily calorie target for weight loss at your chosen pace, plus weeks to your goal — companion to the TDEE calculator.
Daily protein target in grams from body weight, training level, and goal, with a per-meal number.
Lean mass and fat-free mass index from Boer, James, and Hume formulas or a measured body fat percentage.
Estimate VO2 max from a Cooper 12-minute test, heart rate ratio, or a recent race time, with age norms.
Waist divided by hips with WHO risk categories, apple or pear shape, and waist circumference flags.
Measure project materials and costs for home improvement, flooring, room area, concrete slabs, patios, and construction jobs.
How much beer, wine, liquor, ice, and cups you need based on guests, hours, and drink mix.
How many appetizers, ounces of main, sides, and desserts you need per person.
Food quantities, staff count, and total bill (with service charge, tax, gratuity) for any event style.
Area in sq ft, m², and sq yd with waste factor and material cost.
Cubic yards needed for slabs, driveways, and patios — plus bags and cost.
Rolls needed including pattern-repeat waste, doors, and windows.
Tiles and boxes needed with grout joint width and waste buffer.
Gallons of paint needed for a room or surface — adjusts for doors, windows, coats, and ceiling.
Annual kWh production, first-year electric-bill savings, simple payback in years, and 25-year savings from rooftop solar.
Cubic yards, cubic feet, bags, and tons of mulch, gravel, topsoil, or sand to cover a rectangular area at any depth.
Calculate board feet for dimensional lumber. Add multiple sizes for total board feet, lineal feet, waste, and cost.
Sheets of drywall, joint compound, tape, screws, and total material cost for any room.
Roofing squares, shingle bundles, underlayment, ridge cap, and material cost by roof pitch.
Boxes of laminate, hardwood, vinyl plank, or carpet with waste, underlayment, and cost.
Posts, rails, pickets or panels, concrete bags, and cost per linear foot of fence.
Deck boards, joists, beams, footings, fasteners, and cost per square foot.
Batts or blown-in bags by R-value for walls and attics, with depth and total cost.
Bricks or CMU blocks, mortar bags, sand, and cost per square foot of wall.
Tons of asphalt and base gravel for a driveway, plus sealcoating and installed cost.
Tons and cubic yards of gravel for a driveway, plus truck loads, fabric, and delivered cost.
Risers, tread depth, total run, stringer length, and stair angle from total rise, with code checks.
Blocks, courses, caps, base and drainage gravel tons, and material plus installed cost.
Square feet, pallets, and rolls of sod with waste, delivery, installation cost, and watering needs.
Cooling and heating BTU load by room area, insulation, windows, occupancy, and climate zone.
Total wattage, amperage, and breaker size for a room, appliance list, or electrical panel.
Countertop square footage, edge profile, and material plus installation cost by slab price.
Linear feet of baseboard, corner pieces, end caps, and paint or stain cost for any room.
Linear feet of crown molding, corner blocks, coping allowance, and installation cost.
Internal volume and water capacity of PVC, copper, or PEX pipe by diameter and length.
Pavers, edging, base gravel, and sand for a patio, walkway, or driveway with waste and cost.
Required attic ventilation NFA, soffit intake, ridge exhaust, and fan CFM by attic floor area.
Solve common school and study calculations with quick percentage tools and GPA calculators for academic planning.
Three modes: X% of Y, A is what % of B, and % change.
Calculate your semester or cumulative GPA on a 4.0 scale.
Find the GPA you need on remaining coursework to hit a target cumulative GPA.
Add, subtract, multiply, and divide fractions and mixed numbers — results returned simplified, as a mixed number, and as a decimal.
Mean, median, mode, range, sample/population standard deviation, variance, quartiles, IQR, and SEM for any list of numbers.
Weighted course grade from assignments, quizzes, and exams. Shows current grade plus the score needed on remaining work.
Free online scientific calculator with trig, logs, exponents, square roots, parentheses, and constants pi and e.
Find the area of a circle from its radius, diameter, or circumference with the exact formula A = π × r².
Find the circumference of a circle from its radius, diameter, or area using C = 2 × π × r.
Volume and surface area of any cylinder from its radius and height using V = π × r² × h.
Volume and surface area of a sphere from its radius or diameter — uses V = (4/3) × π × r³.
Volume, slant height, and surface area of a cone from base radius and height using V = (1/3) × π × r² × h.
Volume, surface area, and diagonal of a rectangular box from length, width, and height (V = L × W × H).
Mean, median, mode, sum, count, min, max, and range for any list of numbers.
Generate random integers between any minimum and maximum, with or without duplicates — for raffles, drawings, dice rolls, and sampling.
Solve any proportion a/b = c/d for the missing value using cross-multiplication.
Percent change between any old and new value, with the formula and direction shown.
Convert rise and run into decimal slope, percent grade, angle, and 1:N ratio — for ramps, roofs, roads, stairs.
Convert a value to a z-score, percentile, and tail probabilities using the standard normal distribution.
Find P(X<x), P(X>x), and between-range probabilities for any normal distribution with mean μ and SD σ.
Compute P(X=k), cumulative probabilities, mean, and variance for n trials with success probability p.
Model rare events with rate λ — get P(X=k), cumulative probability, mean, and variance.
Compute nPr (order matters) and nCr (order doesn't) with full counting-principle explanation.
Update prior beliefs with new evidence using Bayes' rule — posterior probability with tree diagram.
Compute z or t confidence intervals for a mean, with margin of error breakdown.
One-sample and two-sample t-tests with t-statistic, p-value, and rejection regions.
Goodness-of-fit and independence tests with expected counts, chi-square statistic, and p-value.
Pearson correlation coefficient r with scatter plot, regression line, and interpretation guide.
Least-squares slope, intercept, R², and predictions for any paired (x, y) data.
Required sample size to estimate a proportion or mean at a chosen confidence level and margin of error.
Convert everyday units quickly, including length, weight, volume, and temperature across metric and imperial systems.
Length, weight, and volume between metric and imperial.
Convert between Fahrenheit, Celsius, and Kelvin instantly in either direction.
Convert between m² and ft² — plus square yards, acres, and hectares.
Cups, tablespoons, grams, ounces, and milliliters — plus oven temperature conversions.
MPG from miles and gallons, plus total trip fuel cost at any price per gallon.
Convert kg to lbs and back, plus grams, ounces, and stones-and-pounds.
Convert liters to US and imperial gallons, quarts, pints, fluid ounces, and cubic feet.
Convert feet to meters and back, with centimeters, inches, feet-and-inches, yards, and miles.
Convert °C to °F and back, with Kelvin, Rankine, oven charts, and mental-math shortcuts.
Convert meters to feet and back, with feet-and-inches, centimeters, yards, and total inches.
Convert stone and pounds to kilograms and back, with total pounds and grams.
Convert miles to km and back, plus meters, feet, yards, and nautical miles.
Convert oz to grams and back, with kilograms, pounds-and-ounces, and troy ounces.
Convert millimeters to inches with the nearest 1/16 and 1/32 fraction.
Convert acres to sq ft and back, plus square meters, hectares, and square miles.
Convert between Arabic numbers and Roman numerals — both directions, 1 to 3999, with validation.
Convert shoe sizes between US (men's & women's), UK, European, Japanese (cm), and foot length in centimetres.
Convert milliliters to fluid ounces — covers both US (29.57 ml) and UK Imperial (28.41 ml) fluid ounces.
Convert fluid ounces to cups (US and UK), with tablespoons and milliliters.
Convert inches to centimeters using the exact international factor (1 in = 2.54 cm) — plus mm, m, and feet.
Underwrite commercial real estate by property type — multifamily, hotel, retail, office, and industrial. NOI, cap-rate value, DSCR, and cash-on-cash for brokers, appraisers, and investors.
Pick a property type — multifamily, hotel, retail, office, or industrial — and underwrite it.
Apartment building NOI, cap-rate value, value per door, and DSCR.
ADR × Occupancy × Keys → RevPAR, NOI, and value per key.
Strip center / NNN proforma: rent PSF, CAM recovery, NOI, value per SF.
Office building NOI, rent PSF, expense recoveries, and value per SF.
Warehouse / distribution NOI, NNN rent PSF, and value per SF.
Mixed-use retail + multifamily: per-component NOI, weighted cap rate, value, DSCR.
Mixed-use retail + office: rent PSF, CAM, weighted cap rate, NOI, value, DSCR.
Mixed-use hotel + ground-floor retail: ADR, RevPAR, NNN rent, NOI, value, DSCR.
Three-use mixed-use: hotel, retail, and multifamily rolled into one NOI, value, DSCR.
Capitalization rate from NOI and value, or solve for value, NOI, or required cap rate.
GRM from price and gross rent, or solve price or rent — with the implied cap rate and 1% rule.
NOI divided by loan amount, or the maximum loan a target debt yield supports — with DSCR and LTV.
LTV, CLTV, down payment, and the paydown needed to drop mortgage insurance.
Price per square foot or meter, total price, or size — plus a comparable-sale check.
All-in cost, refinance proceeds, cash left in the deal, cash flow, DSCR, and cash-on-cash.
Fix-and-flip profit, ROI, annualized return, break-even resale, and 70% rule max offer.
After repair value from comps and price per square foot, with a 70% rule max offer.
What you walk away with: payoff, commission, closing costs, prorations, and net proceeds.
Max home price from income using 28/36 and 31/43 DTI limits, with full PITI breakdown.
Occupancy needed to cover opex and debt service, plus break-even rent and DSCR.
Base rent, CAM, taxes and insurance, escalations, free rent, TI, and net effective rent.
Commission by price and rate, side splits, agent-broker splits, fees, and agent net.
Annual cash flow divided by cash invested — the levered return on a rental property.
Gross and net rental yield from purchase price, monthly rent, expenses, and vacancy.
Maximum offer for a flip — 70% of ARV minus repairs, with adjustable spread for any market.
Commercial mortgage payment with DSCR, interest-only period, balloon balance, and max loan sizing.
Estimate your property tax bill with state and county millage lookups, exemptions, and a 5-year projection.
Buyer closing-cost breakdown by line item — lender, title, government, prepaids — plus cash-to-close.
Deferred gain, recognized boot from cash and debt relief, federal tax owed, and carryover basis on a like-kind real estate exchange.
Cash boot, mortgage boot, and the tax owed on a partial 1031 exchange when you buy down in price or debt.
45-day identification and 180-day completion deadlines for a 1031 like-kind exchange from any closing date.
Underwrite a self-storage facility: NRSF, GPI, vacancy, NOI, cap-rate value, and value per square foot and per unit.
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