Tallytopia
Free online calculators with a transparent, editable breakdown — change any input and everything recalculates instantly.
73 calculators across finance, health, math, home & diy, sports, space and everyday — each one shows its formula step by step, cites its sources, and is checked against known values before every release (see how our calculators work).
Just need to crunch numbers? Open the scientific calculator — or count anything with the tally counter.
Popular
- Mortgage Payment CalculatorWork out the monthly payment on a fixed-rate mortgage from the loan amount, interest rate and term.
- Compound Interest CalculatorSee how a lump sum grows over time with compound interest, at any compounding frequency.
- Loan Repayment CalculatorMonthly repayment on a personal or car loan from the amount, interest rate and term.
- Savings Goal CalculatorHow long it takes to reach a savings goal at a given monthly contribution and interest rate.
- Break-Even CalculatorHow many units you must sell to cover your fixed costs, from price and variable cost.
- Salary to Hourly CalculatorConvert an annual salary into its hourly, weekly and monthly equivalents.
- Markup & Margin CalculatorProfit, markup and margin from a product's cost and selling price — and why markup and margin differ.
- VAT CalculatorAdd VAT to a net price: see the VAT amount and the gross (VAT-inclusive) total.
- Irish VAT CalculatorAdd Irish VAT to a net price at the 23% standard rate — or any reduced rate.
- BTW Calculator (Netherlands VAT)Add Dutch BTW to a net price at the 21% standard rate — or the 9% reduced rate.
- MwSt Calculator (German VAT)Add German MwSt to a net price at the 19% standard rate — or the 7% reduced rate.
- TVA Calculator (French VAT)Add French TVA to a net price at the 20% standard rate — or the 10%, 5.5% or 2.1% reduced rates.
- South African VAT CalculatorAdd South African VAT to a price at the 15% standard rate.
- Australian GST CalculatorAdd Australian GST to a price at the 10% rate — see the GST amount and the total.
- New Zealand GST CalculatorAdd New Zealand GST to a price at the 15% rate — see the GST amount and the total.
- India GST CalculatorAdd Indian GST to a price at the 18% standard slab — or any of the 5%, 12% or 28% slabs.
- Sales Tax CalculatorAdd US sales tax to a price — enter your combined state and local rate.
- BMI CalculatorCalculate your body mass index (BMI) from your weight and height.
- BMR CalculatorEstimate your basal metabolic rate — the calories your body burns at complete rest.
- TDEE Calculator — Daily Calorie NeedsEstimate the calories you burn per day from your BMR and activity level.
- Ideal Weight CalculatorEstimate an ideal body weight from height and sex using the Devine formula.
- Water Intake CalculatorA daily drinking-water estimate from your body weight and exercise time.
- Body Fat Calculator (US Navy Method)Estimate body fat percentage from tape measurements using the US Navy circumference formula.
- Macro CalculatorSplit daily calories into grams of protein, carbs and fat at your chosen percentages.
- One Rep Max CalculatorEstimate your one-rep max from a weight and rep count, with common training percentages.
- Pregnancy Due Date CalculatorEstimate a due date from the first day of the last menstrual period, adjusted for cycle length.
- Ovulation CalculatorEstimate your ovulation date and fertile window from your last period and cycle length.
- Pythagorean Theorem CalculatorFind the hypotenuse of a right triangle from its two legs — plus area and perimeter.
- Circle CalculatorArea, circumference and diameter of a circle from its radius.
- Triangle Area CalculatorThe area of any triangle from its base and height.
- Quadratic Formula CalculatorSolve ax² + bx + c = 0 — both roots and the discriminant, step by step.
- Slope CalculatorSlope, y-intercept and distance between two points on a line.
- Exponent CalculatorRaise any base to any power, including negative and fractional exponents.
- Root CalculatorSquare roots, cube roots and any nth root of a number.
- Percent Error CalculatorHow far a measured value is from the true value, as a percentage.
- GCF & LCM CalculatorGreatest common factor and least common multiple of two numbers.
- Combinations & Permutations CalculatorHow many ways to choose or arrange r items from a set of n.
- Z-Score CalculatorHow many standard deviations a value sits above or below the mean.
- Square Footage CalculatorThe square footage of a room or area from its length and width — with square yards and square meters.
- Concrete CalculatorConcrete for a slab: cubic yards to order, or how many 80 lb and 60 lb bags to buy.
- Paint CalculatorHow many gallons of paint a room needs, from wall length, height, doors and windows.
- Roofing CalculatorRoof area, roofing squares and shingle bundles from the house footprint and roof pitch.
- Tile CalculatorHow many tiles a floor or wall needs, by tile size, with waste included.
- Mulch CalculatorCubic yards or bags of mulch for a bed, from its area and depth.
- Gravel CalculatorCubic yards and tons of gravel for a driveway or path, from area and depth.
- Space Travel Time CalculatorHow long would it take to reach the Moon, Mars or Neptune — by car, by rocket, or at Voyager speed?
- Weight on Other Planets CalculatorWhat would you weigh on the Moon, Mars or Jupiter? Your weight scaled by each world's surface gravity.
- Age on Other Planets CalculatorHow old would you be in Mercury years or Mars years? Your age converted to another planet's trips around the Sun.
- Orbital Period Calculator (Earth Satellites)How long a satellite takes to circle the Earth, from its altitude — the ISS laps the planet in about 93 minutes.
- Escape Velocity CalculatorThe speed needed to break free of a world's gravity, from its mass and radius — in Earth units, so any planet works.
- Light Travel Time CalculatorHow long light takes to cross space — 1.3 seconds to the Moon, 8 minutes from the Sun, 4 years from the nearest star.
- Telescope Magnification CalculatorMagnification and true field of view from your telescope's focal length and any eyepiece.
- Distance Between Planets CalculatorHow close two planets get and how far apart they can be, from their average distances to the Sun.
- 1g Space Travel CalculatorHow fast you'd cross the solar system accelerating at 1g the whole way — Mars in two days, with Earth-like gravity aboard.
- Running Pace CalculatorYour pace per km and per mile from any distance and finish time — plus your speed in km/h.
- Race Time PredictorPredict your 10K, half or marathon time from a recent race, using Riegel's endurance formula.
- Heart Rate Zones CalculatorYour five training zones from age and resting heart rate, using the Karvonen (heart rate reserve) method.
- Calories Burned CalculatorCalories burned by activity, weight and time, using standard MET values for common exercises.
- Treadmill Pace ConverterConvert treadmill speed in km/h to pace per kilometre and per mile — and to mph.
- Steps to Km & Miles CalculatorHow far your steps take you — convert a step count into kilometres and miles from your stride length.
- VO₂ Max Calculator (Cooper Test)Estimate your VO₂ max from how far you can run in 12 minutes — the classic Cooper field test.
- Tip CalculatorWork out the tip, the total bill, and each person's share when splitting.
- Coin Counter Calculator (US)Count a pile of US coins into dollars: enter how many quarters, dimes, nickels and pennies you have.
- Words to Minutes — Speech Time CalculatorHow long a speech or presentation takes to deliver, from its word count and your speaking pace.
- Percentage CalculatorWork out what X% of a value is — discounts, tips, statistics, anything.
- Percentage Change CalculatorThe percentage increase or decrease from one value to another.
- Discount CalculatorSee the sale price and how much you save from a percentage discount.
- Fuel Cost CalculatorThe fuel cost of a trip from distance, consumption (L/100km) and fuel price.
- Electricity Cost CalculatorWhat an appliance costs to run, from its wattage, daily use and your electricity price.
- Final Grade CalculatorWhat score do you need on the final exam to reach your target grade?
- Age CalculatorYour exact age in years, months and days — and your total days alive.
- Days Between Dates CalculatorCount the days, weeks and calendar months between any two dates.
- Date Calculator — Add or Subtract DaysWhat date is 90 days from today? Add or subtract days, weeks, months or years from any date.
Frequently asked questions
Are these calculators free to use?
Yes — every calculator on Tallytopia is free, with no account, no sign-up and no usage limits. You can even embed any calculator on your own site for free.
How do the calculators work?
Each calculator is a transparent formula run by one deterministic calculation engine: you see every intermediate step, and changing any input recalculates everything instantly. The formulas and their sources are documented on our methodology page.
How accurate are the results?
Calculations use published standard formulas at full precision, and an automated test suite pins results to independently known values before any change goes live. Results are informational only — not financial, medical or legal advice.
Can I ask a question in plain English?
Yes — type a question like "monthly payment on a $450k loan at 6% over 25 years" into the box above, and it opens the right calculator with your numbers already filled in.