Free Online Calculators & Everyday Math Tools

Compare A/B conversion rates with a two-proportion significance test and confidence interval.

Calculate age in years, months and days, total days lived and the next birthday from two calendar dates.

Calculate elapsed age in days, hours and minutes from a date of birth.

Convert a nominal annual percentage rate into an effective annual yield for a selected compounding frequency.

Find your current attendance rate and estimate how many future sessions you can miss while meeting a target.

Estimate monthly auto-loan payments, total interest and payoff amount from price, down payment, APR and term.

Calculate average speed from distance and travel time in kilometres per hour and miles per hour.

Convert up to 1,000 Unix timestamps to ISO UTC dates. Explicitly choose seconds or milliseconds and retain each source value.

Split a restaurant or group bill evenly and add an optional tip percentage.

Calculate exactly, at most or at least k successes in n independent trials, with expected value and standard deviation.

Illustrative BAC estimate from drink amounts, body weight and elapsed time; never use for driving decisions.

Classify a blood-pressure reading using adult U.S. AHA categories and show when to seek urgent help. A single reading is not a diagnosis.

Calculate body mass index from height and weight using metric units, with the standard adult category ranges.

Estimate body-fat percentage with the US Navy tape-measure method and unit selection.

Find the units and sales revenue needed to cover fixed costs using selling price and variable cost per unit.

Count working days between dates with selectable weekends, optional end-date inclusion and your own holiday list.

Convert between bytes, KB, MB, GB, TB, PB. Binary (1024) and decimal (1000) standards.

Calculate an estimated auto loan payment from vehicle price, down payment, sales tax, interest rate and term.

IPv4 subnet calculator — mask, wildcard, network/broadcast addresses, host range, and classification.

Calculate ad, email or search result click-through rate from clicks and impressions.

Project a balance with an initial amount, monthly contributions and monthly compounding. See contributions and growth year by year.

Estimate concrete volume and bag count for a slab using length, width, depth and bag yield.

Estimate concrete volume and bag count for stairs using step width, rise, run and number of steps.

Calculate website or campaign conversion rate from visitors and completed goals.

Convert cups, tablespoons, teaspoons, millilitres, grams and ounces for common baking and cooking ingredients.

Find average advertising cost per new customer, signup or other acquisition goal.

Create a shareable countdown link to a date and time; the countdown runs in the open browser.

Estimate how long a fixed monthly payment will take to clear a credit card balance and how much interest it may add.

Build five-field Unix cron schedules for intervals, daily runs, weekdays, weekly or monthly jobs, with validated custom numeric fields.

Translate any cron expression to plain English and preview the next five executions in your timezone.

Convert money between major currencies using the latest available reference exchange rates. Rates are retrieved when you convert.

Compare the amount received after a provider exchange-rate markup and fixed or percentage fees.

Estimate curtain fabric width from window dimensions, heading style, fullness and fabric repeat.

Estimate simple customer lifetime value from average order value, purchase frequency and retention.

Estimate resting energy and daily maintenance calories for adults using age, height, weight and activity level.

Find a date by adding or subtracting a chosen number of days, weeks, months or years from a starting date.

Calculate signed calendar days, full weeks and remaining days between two dates without daylight-saving surprises.

Convert human-readable dates to Unix timestamps and timestamps back to readable dates.

Estimate payoff time, total interest and payment schedule for a fixed-rate balance and monthly payment.

Calculate monthly debt-to-income ratio from gross income and recurring monthly debt obligations.

Estimate deck board count and total linear metres from deck dimensions, board width, gap and board length.

Calculate a sale price and how much you save from an original price and percentage discount. Supports common currencies.

Calculate the monthly savings needed to reach a home down-payment goal by a target date.

Estimate transfer time from file size, bandwidth and efficiency, with explicit decimal/binary size units and bit-per-second network units.

Estimate the monthly electricity cost of an appliance from watts, daily hours and your price per kWh.

Estimate device electricity use and cost from watts, daily runtime, billing period and tariff.

Calculate delivered-email open, click and unsubscribe rates from one campaign’s aggregate counts.

Set a savings target from essential monthly expenses, a chosen number of months and your current reserve.

Estimate fence post count from fence length and post spacing, including posts at both ends.

Find the final-exam percentage needed to reach your target course grade. Includes weighted coursework and an attainable-target check.

Calculate floor area, add a cutting allowance and estimate how many flooring packs to buy.

Add, subtract, multiply and divide fractions with exact BigInt arithmetic. Return a simplified fraction and decimal approximation.

Estimate a billable hourly rate from an annual income goal, business costs and realistic billable hours.

Estimate trip fuel use and cost from distance, vehicle consumption and fuel price.

Convert fuel economy between MPG, US MPG, UK MPG, kilometres per litre and litres per 100 kilometres.

Estimate driving distance from usable fuel volume and your vehicle’s fuel consumption.

Estimate soil volume and bags for raised beds or planters from their dimensions and fill depth.

Find the greatest common divisor and least common multiple of a list of whole numbers using exact integer arithmetic.

Calculate a credit-weighted GPA from course grades. Enter letter grades or numeric grade points in an editable course table.

Find the score needed on a final exam to reach a target course grade based on your current grade and exam weight.

Estimate gravel volume and approximate tonnes from the area, depth and bulk density.

Convert an hourly wage into estimated weekly, monthly and annual gross pay using work hours and paid weeks.

Estimate a room air-conditioner capacity from floor area and user-entered adjustment factors.

Validate IBAN structure and MOD-97 checksum locally; identify the country code and length.

Create a downloadable .ics calendar event with explicit timezone offsets, UTC timestamps, location and description, without sending invitations.

Compare several adult height-based reference formulas. These are rough population estimates, not personal health targets.

Estimate future cost or the future equivalent of today’s amount using an assumed annual inflation rate.

Compare purchasing power across years using an assumed average annual inflation rate.

Project compound investment growth with an initial balance, recurring contributions, return and compounding frequency.

Estimate investment return after contributions, dividends, inflation and an assumed tax rate.

Convert dotted IPv4 addresses to unsigned 32-bit decimal values and back, with hexadecimal and binary representations.

Validate IPv6 addresses and show expanded, compressed and integer representations, including IPv4-mapped input.

Find a date’s ISO week number, ISO week-year, weekday and the Monday–Sunday boundaries of its week.

Estimate a fixed-rate loan payment, total interest and payoff time when you add an extra monthly amount.

Estimate a fixed-rate monthly loan payment, total interest and amortization schedule. Enter an amount, annual rate and term in months.

Estimate daily protein, carbohydrate and fat targets from calories and a selected fitness goal.

Transpose matrices, multiply two matrices or calculate a determinant from JSON arrays. Supports numeric matrices up to 10 × 10.

Find the mean, median, mode and range of a list of numbers for homework, reports and quick data checks.

Estimate the labor cost of a meeting from attendee count, hourly rates and meeting duration.

Compare take-home income with common monthly spending categories and a savings goal.

Estimate a home price range from gross monthly income, monthly debts, a payment ratio and loan assumptions.

Estimate monthly mortgage principal and interest, plus property tax, home insurance and HOA costs.

Estimate moving expenses from truck, movers, packing, travel and other costs, with an optional contingency.

Work out mulch volume and the number of bags for a garden bed based on area and depth.

Estimate personal net worth by totaling assets and subtracting debts and other liabilities.

Convert integers between binary, octal, decimal, and hexadecimal with BigInt precision.

Spell signed whole numbers in English using exact decimal input, from zero through eighteen-digit magnitudes.

Estimate one-repetition maximum with Epley and Brzycki formulas from a submaximal lift.

Run a live countdown or stopwatch with start, pause, resume, reset and stopwatch laps. Works locally in your browser.

Convert oven temperatures between Celsius, Fahrenheit and gas mark for recipes from different countries.

Estimate gross weekly pay with a regular-hours threshold and an overtime pay multiplier.

Estimate a fertile-window date range from the last period and cycle length. Calendar estimates cannot predict ovulation reliably.

Estimate how many litres of paint you need from wall area, number of coats, coverage and a waste allowance.

Convert common ISO A-series, US Letter and Legal paper sizes between millimetres, inches and print pixels.

Calculate your new salary and increase after a percentage raise, with equivalent monthly and weekly pay.

Estimate a U.S. paycheck after federal income tax, Social Security and Medicare using 2026 federal brackets. State and local taxes are excluded.

Generate upcoming weekly, biweekly or monthly payday dates from your next payday.

Calculate a percentage of a number, one value as a percentage of another, or percentage increase and decrease with clear formulas.

Compare an observed value with a reference value and calculate absolute error and relative percentage error.

Calculate the percentage-point difference and relative percentage change between two rates.

Format a phone number as international E.164 or national display using a selected country calling code.

Run configurable focus and break intervals and track completed Pomodoro sessions in this browser.

Estimate a pregnancy due date from the last menstrual period or conception date.

Estimate gestational week and day from the last menstrual period date. Confirm dating with a clinician.

Find prime factors, exponents and primality for whole numbers from 2 to one trillion. All calculations stay in your browser.

Calculate gross profit, profit margin and markup from cost and selling price, or find a selling price for a target margin.

Calculate a partial-month rent amount from the monthly rent, days in that month and days charged.

Solve ax² + bx + c = 0 for real, repeated or complex roots. Handles linear and degenerate equations explicitly.

Generate random integers in a range, with no repeats when the range allows. Runs locally using the browser crypto API.

Estimate total recipe cost and cost per serving from ingredient spend, servings and optional extra costs.

Scale ingredient quantities to a new number of servings. Edit ingredients in a table; supports decimals, fractions and mixed numbers.

Estimate a monthly rent budget using gross income, recurring debt and a chosen housing-cost percentage.

Compare estimated renting and homeownership costs over a chosen period using your own assumptions.

Project retirement savings from current balance, recurring contributions, years and an assumed annual return.

Calculate return on ad spend from attributed revenue and advertising cost.

Convert whole numbers from 1 to 3999 into Roman numerals or validate and decode canonical Roman numeral text.

Calculate running pace per kilometre and mile, speed and estimated finish time from distance and elapsed time.

Estimate take-home salary from gross pay using a country selection and an explicitly simplified tax model.

Convert annual salary into estimated hourly, weekly and monthly pay using your work schedule.

Calculate sales commission and total gross pay from sales, a commission rate and optional base pay.

Add sales tax to a price or break the tax amount out of a tax-inclusive total.

Estimate how many months it will take to reach a savings target from your current balance and monthly deposit.

Project savings growth with an initial balance, recurring monthly deposits, an annual rate and a time horizon.

Convert decimal or exponent notation into normalized scientific notation and an exact expanded decimal string.

Estimate organic search revenue and ROI from visits, conversion rate, order value and SEO cost.

Calculate simple interest and total value from principal, annual rate and time.

Estimate bedtime or wake-up options using common 90-minute sleep-cycle intervals and time to fall asleep.

Calculate floor area for rectangular rooms and add multiple room measurements for a project estimate.

Calculate population or sample standard deviation and variance from a list of values.

Run a two-sided one-sample z test for a proportion and explain the p-value and decision threshold.

Total recurring subscriptions by month and year, including weekly, quarterly and annual billing.

Estimate 2026 U.S. federal income tax by filing status and taxable income, showing marginal and effective rates. State tax and credits are excluded.

Calculate a test percentage, points missed and points needed to reach a target score.

Estimate tile quantity from room dimensions, tile size and a cutting allowance before a renovation.

Convert durations between milliseconds, seconds, minutes, hours, days and weeks, with a readable days-hours-minutes-seconds breakdown.

Convert an explicitly offset ISO timestamp to an IANA time zone with the correct date and daylight-saving offset.

Compare a proposed meeting time across selected IANA time zones in the browser.

Calculate a tip, total bill and each person’s share. Split remaining cents fairly so all shares add up to the exact total.

Split a restaurant bill, add a tip and assign different amounts or shares to each person.

Estimate a trip budget from travel costs, daily lodging, meals, activities and a contingency.

Estimate fuel needed and cost for a trip using distance, fuel consumption and price per litre.

Convert length, mass, volume and temperature between metric and common imperial units with clear unit compatibility checks.

Compare the cost per kilogram, litre, item or other unit for two products to find the better value.

Add VAT to a net price or extract VAT from a VAT-inclusive total using your entered rate.

Estimate wallpaper rolls from wall width, wall height, roll size and pattern repeat.

Estimate a daily fluid starting point from body weight and activity; not medical advice.

Add major wedding costs and a per-guest catering estimate to see the total and remaining budget.

Calculate a weighted mean from CSV values and weights, with explicit handling of zero weights and invalid rows.

Calculate shift length and paid work hours from clock-in, clock-out and an unpaid break, including overnight shifts.