Everyday calculators

Find your exact age in years, months and days, total days and weeks lived, your next birthday, the day of the week you were born and your zodiac sign.

The exact gap between two birth dates in years, months and days, both ages, and the 'half your age plus seven' range — with an honest note on what it is worth.

Your ideal sleep and wake times from chronotype and sleep need, plus the social jetlag between your workday and free-day schedules, using the MCTQ mid-sleep method.

How much car you can afford on the 20/4/10 rule — 20% down, 4-year loan, 10% of income — with insurance, fuel and maintenance counted inside the budget.

Coffee-to-water ratios for drip, pour-over, French press, espresso and cold brew — enter the water or the coffee and get the other, with a strength adjustment.

Budget a concrete slab line by line — ready-mix, gravel base, rebar, forms, labour and contingency — with every unit price left as an input you set locally.

Roasting time for beef, pork, chicken and turkey by weight and doneness from the USDA charts, plus the safe internal temperature that really decides it.

How many days until any date or holiday, with weeks, hours, weekends and working days too. Pick a holiday or a birthday and it counts to the next one.

Count the days, weeks, months and business days between two dates, or add and subtract days, weeks, months or years from any date — leap years handled exactly.

What day of the week a date falls on, plus its day number in the year, ISO week number, leap-year status, and that date's weekday in nearby years.

Dew point from temperature and relative humidity using the Magnus formula with WMO coefficients, plus absolute humidity, vapour pressure and a comfort reading.

Find the sale price and savings for any percent off, stack a second discount, add sales tax, or work backwards from a sale price to the percentage off.

Find what any appliance costs to run per day, month and year from its wattage, hours of use and your price per kWh — plus a table of common appliances at your rate.

How long an EV takes to charge and what it costs, from battery size, start and target state of charge, charger power and charging efficiency.

Cost per mile for an electric car against a gas one, from electricity and fuel prices and real efficiency — with annual savings and the break-even gas price.

Estimate a trip's gas cost from distance, your MPG or L/100 km and the price per gallon or liter — with fuel needed, cost per mile and the split per passenger.

Plan a holiday or wedding gift budget by tier: how many people, how much each, a running total against your ceiling, and the per-gift amounts that would fit.

Heat index (apparent temperature) from temperature and humidity using the NWS Rothfusz regression with both adjustments, plus the NWS risk category.

Timesheet calculator: hours worked between start and end times minus breaks, per day, week and pay period, with gross pay. Handles overnight shifts.

How long jet lag lasts for your flight, why flying east hurts more, and a day-by-day light-exposure plan built on your body clock's temperature minimum.

What a load of laundry really costs: machine electricity, water heating, water and sewer, drying and detergent, the annual total, and what line drying would save.

Calculate your car's real fuel economy from miles driven and gallons used — or from two odometer readings at fill-up — in US mpg, UK mpg, L/100 km and km/L.

Compare up to three pizzas by area instead of diameter. A 16-inch is not twice a 12-inch — it is 1.78 times — and price per square inch shows which deal really wins.

Estimate how long a text takes to read from its word count or page count at slow, average (238 wpm), fast or custom speeds — plus the time to read it aloud.

Scale a recipe up or down by servings, with each ingredient rounded to real measuring-spoon fractions — and a straight answer on what doesn't scale.

Turn daily and weekly screen hours into days per year and a share of your waking life, and see what cutting fifteen minutes a day would actually give back.

Split a bill evenly between any number of people with tip included, or give one person a bigger or smaller share — see exactly what each person owes.

Add or subtract two durations in hours, minutes and seconds and get the result as h:mm:ss, decimal hours, total minutes and total seconds — with the carrying shown.

A weekly timesheet: seven days of clock-in and clock-out times with breaks, regular and overtime hours split at your threshold, gross pay, and overnight shifts.

The exact time between two dates and times in days, hours, minutes and total seconds, plus the working hours it covers under your own working-day definition.

Convert a date and time between world time zones using real IANA zone data, so daylight saving is applied correctly rather than a fixed, half-wrong offset.

Work out the tip and total for any bill, split it between people, round the total up, and tip on the pre-tax amount — with a 15–25% comparison table.

Split a restaurant bill when everyone ordered differently: tax and tip apportioned in proportion to what each person had, with the cents adding up exactly.

Compare two P-metric tire sizes: overall diameter, sidewall height, circumference, revolutions per mile, and the speedometer error a size change introduces.

Compare up to three package sizes on price per ounce, litre or item — even in mixed units — and see which is actually cheaper and by how much.

Annual water heating cost from household size, water temperature and energy price, comparing electric, gas and heat-pump units by their Uniform Energy Factor.

Wind chill from air temperature and wind speed using the 2001 NWS formula, with frostbite times and an honest note about where the formula stops applying.