Free calculators, grouped by what you need

Countdown to any future date — birthdays, holidays, deadlines.

Add or subtract days, weeks, months, years, or business days from any date.

Days, weeks, months, and years between any two dates — with optional business-days-only count.

Count business days between two dates or add/subtract working days from any date, with custom holidays excluded.

Add up hours worked between start and end times, minus breaks.

Convert any date and time between time zones — DST aware.

Count business days between two dates or add/subtract working days from any date, with custom holidays excluded.

Drift-free stopwatch with laps and a countdown timer with audible alert — millisecond accuracy.

Your exact age in years, months, days, hours, and minutes.

Countdown to any future date — birthdays, holidays, deadlines.

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.

Your exact age in years, months, days, hours, and minutes.

What date is 30, 60, or 90 days from today? Calendar days or business days, with day of the week.

How long it's been since any date — years, months, days, hours, minutes, and live-ticking seconds. Birthdays, quit dates, milestones.

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.

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.

Your exact age in years, months, days, hours, and minutes.

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.

Home equity line of credit: max borrow, interest-only payment, and full repayment cost.

Monthly payment and total interest for any personal or auto loan.

Monthly car payment including tax, trade-in, and down payment.

How long it takes — and how much interest you'll pay — at your current monthly payment.

Home equity line of credit: max borrow, interest-only payment, and full repayment cost.

Project your retirement balance with employer match and growth.

Project your investment growth over years or decades.

Total return, profit, and annualized CAGR for any investment.

Convert between APR and APY for any compounding frequency.

Estimate take-home pay after federal, state, and FICA taxes.

Annual and biweekly net pay after federal, FICA, and state income tax — all 50 states plus DC.

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.

Calculate tips and split the bill between any number of people.

Find the sale price after any percentage discount.

Add sales tax, GST, HST, or VAT to any price and see the final total.

What a dollar from any year is worth today — adjust for the inflation rate.

Live exchange rates between major world currencies — updated daily (ECB).

Salary you need in another city to maintain the same standard of living.

How much to save monthly to hit any goal by a target date.

Add up assets, subtract liabilities, see your total net worth.

Project your investment growth over years or decades.

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 much to save monthly to hit any goal by a target date.

Compare snowball vs avalanche payoff — time, interest, and which finishes first.

Project tax-free Roth IRA growth to retirement and compare it against a taxable account.

Project your retirement balance with employer match and growth.

Project your investment growth over years or decades.

Total return, profit, and annualized CAGR for any investment.

Profit margin, markup, and revenue from any combination of cost, selling price, and target margin.

Estimate capital gains tax on stocks or property with basis, holding period, recapture, and state tax.

Standard wedding budget breakdown across venue, catering, photo, attire, flowers, music, and more.

How much to save monthly to hit any goal by a target date.

Find the sale price after any percentage discount.

Capitalization rate from NOI and value, or solve for value, NOI, or required cap rate.

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.

Apartment building NOI, cap-rate value, value per door, and DSCR.

Income, expenses, cap-rate value, cash flow, sale proceeds, and leveraged IRR.

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.

Underwrite a self-storage facility: NRSF, GPI, vacancy, NOI, cap-rate value, and value per square foot and per unit.

Maximum offer for a flip — 70% of ARV minus repairs, with adjustable spread for any market.

Deferred gain, recognized boot from cash and debt relief, federal tax owed, and carryover basis on a like-kind real estate exchange.

Buyer closing-cost breakdown by line item — lender, title, government, prepaids — plus cash-to-close.

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.

GRM from price and gross rent, or solve price or rent — with the implied cap rate and 1% rule.

Price per square foot or meter, total price, or size — plus a comparable-sale check.

After repair value from comps and price per square foot, with a 70% rule max offer.

Capitalization rate from NOI and value, or solve for value, NOI, or required cap rate.

LTV, CLTV, down payment, and the paydown needed to drop mortgage insurance.

NOI divided by loan amount, or the maximum loan a target debt yield supports — with DSCR and LTV.

Commercial mortgage payment with DSCR, interest-only period, balloon balance, and max loan sizing.

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.

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.

Maximum offer for a flip — 70% of ARV minus repairs, with adjustable spread for any market.

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.

Commission by price and rate, side splits, agent-broker splits, fees, and agent net.

Buyer closing-cost breakdown by line item — lender, title, government, prepaids — plus cash-to-close.

Estimate your property tax bill with state and county millage lookups, exemptions, and a 5-year projection.

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.

Max home price from income using 28/36 and 31/43 DTI limits, with full PITI breakdown.

Price per square foot or meter, total price, or size — plus a comparable-sale check.

Estimate your property tax bill with state and county millage lookups, exemptions, and a 5-year projection.

Body mass index in metric or US units, with category.

Estimate body fat percent with the US Navy circumference method, plus a BMI-based check.

Models the body as an ellipse from waist and height — predicts mortality risk better than BMI.

Keep your waist under half your height — the simple cardiometabolic risk screen.

Estimate ideal body weight from height, sex, and frame using Hamwi, Devine, Robinson, and Miller formulas, plus the healthy-BMI range.

Daily calories to lose, maintain, or gain weight using Mifflin-St Jeor.

Daily calorie target for weight loss at your chosen pace, plus weeks to your goal — companion to the TDEE calculator.

Basal metabolic rate using Mifflin-St Jeor and Harris-Benedict, with activity-multiplier TDEE.

Daily protein, carbs, and fat targets for cutting, maintenance, or bulking based on your TDEE.

How many ounces, cups, or liters you should drink each day.

Pace per mile/km and average speed from time and distance.

Estimate your 1RM from a working set using Epley, Brzycki, Lombardi, O'Conner, and Lander formulas.

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.

Estimate your due date and current week of pregnancy.

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.

Best bedtime or wake time based on 90-minute sleep cycles.

How many ounces, cups, or liters you should drink each day.

Convert your daily step count to miles and kilometers — see both at once.

Turn your step count into calories burned using MET values, body weight, stride length, and pace.

Pace per mile/km and average speed from time and distance.

Estimate VO2 max from a Cooper 12-minute test, heart rate ratio, or a recent race time, with age norms.

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.

Daily protein, carbs, and fat targets for cutting, maintenance, or bulking based on your TDEE.

Estimate your 1RM from a working set using Epley, Brzycki, Lombardi, O'Conner, and Lander formulas.

Waist divided by hips with WHO risk categories, apple or pear shape, and waist circumference flags.

Keep your waist under half your height — the simple cardiometabolic risk screen.

Body mass index in metric or US units, with category.

Estimate body fat percent with the US Navy circumference method, plus a BMI-based check.

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.

Weighted course grade from assignments, quizzes, and exams. Shows current grade plus the score needed on remaining work.

Three modes: X% of Y, A is what % of B, and % change.

Percent change between any old and new value, with the formula and direction shown.

Mean, median, mode, sum, count, min, max, and range for any list of numbers.

Solve any proportion a/b = c/d for the missing value using cross-multiplication.

Convert rise and run into decimal slope, percent grade, angle, and 1:N ratio — for ramps, roofs, roads, stairs.

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.

Free online scientific calculator with trig, logs, exponents, square roots, parentheses, and constants pi and e.

Generate random integers between any minimum and maximum, with or without duplicates — for raffles, drawings, dice rolls, and sampling.

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).

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.

Length, weight, and volume between metric and imperial.

Convert between m² and ft² — plus square yards, acres, and hectares.

Convert inches to centimeters using the exact international factor (1 in = 2.54 cm) — plus mm, m, and feet.

Convert feet to meters and back, with centimeters, inches, feet-and-inches, yards, and miles.

Convert meters to feet and back, with feet-and-inches, centimeters, yards, and total inches.

Convert °C to °F and back, with Kelvin, Rankine, oven charts, and mental-math shortcuts.

Convert millimeters to inches with the nearest 1/16 and 1/32 fraction.

Convert shoe sizes between US (men's & women's), UK, European, Japanese (cm), and foot length in centimetres.

Cups, tablespoons, grams, ounces, and milliliters — plus oven temperature conversions.

Convert between Fahrenheit, Celsius, and Kelvin instantly in either direction.

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.

MPG from miles and gallons, plus total trip fuel cost at any price per gallon.

Convert miles to km and back, plus meters, feet, yards, and nautical miles.

Convert between Arabic numbers and Roman numerals — both directions, 1 to 3999, with validation.

Convert acres to sq ft and back, plus square meters, hectares, and square miles.

Convert between m² and ft² — plus square yards, acres, and hectares.

Convert kg to lbs and back, plus grams, ounces, and stones-and-pounds.

Convert oz to grams and back, with kilograms, pounds-and-ounces, and troy ounces.

Convert stone and pounds to kilograms and back, with total pounds and grams.

Convert liters to US and imperial gallons, quarts, pints, fluid ounces, and cubic feet.

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.

Gallons of paint needed for a room or surface — adjusts for doors, windows, coats, and ceiling.

Rolls needed including pattern-repeat waste, doors, and windows.

Tiles and boxes needed with grout joint width and waste buffer.

Cubic yards needed for slabs, driveways, and patios — plus bags and cost.

Calculate board feet for dimensional lumber. Add multiple sizes for total board feet, lineal feet, waste, and cost.

Cubic yards, cubic feet, bags, and tons of mulch, gravel, topsoil, or sand to cover a rectangular area at any depth.

Area in sq ft, m², and sq yd with waste factor and material cost.

Annual kWh production, first-year electric-bill savings, simple payback in years, and 25-year savings from rooftop solar.

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.

Sheets of drywall, joint compound, tape, screws, and total material cost for any room.

Batts or blown-in bags by R-value for walls and attics, with depth and total cost.

Gallons of paint needed for a room or surface — adjusts for doors, windows, coats, and ceiling.

Rolls needed including pattern-repeat waste, doors, and windows.

Roofing squares, shingle bundles, underlayment, ridge cap, and material cost by roof pitch.

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.

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.

Blocks, courses, caps, base and drainage gravel tons, and material plus installed cost.

Risers, tread depth, total run, stringer length, and stair angle from total rise, with code checks.

Square feet, pallets, and rolls of sod with waste, delivery, installation cost, and watering needs.

Boxes of laminate, hardwood, vinyl plank, or carpet with waste, underlayment, and cost.

Tiles and boxes needed with grout joint width and waste buffer.

Bricks or CMU blocks, mortar bags, sand, and cost per square foot of wall.

Cubic yards needed for slabs, driveways, and patios — plus bags and cost.