Everyday calculators
Percentages, discounts, dates, units, fuel, paint and concrete.
Calculator
Type a calculation or tap it in on the keypad. The answer updates as you go, and = puts it back in the box so you can keep going.
Percentage calculator
Pick the question, enter X and Y, and read the answer with the formula used.
Discount calculator
Enter the original price and the discount to see the sale price and what you save, then stack a second coupon or add tax for the checkout total.
Sales tax calculator
Enter a price and pick a state to see the tax and total, or switch the mode to pull the tax out of a price that already includes it.
Unit converter
Enter a value and pick the units for length, weight, kitchen volumes and temperature, using exact definitions rather than rounded approximations.
Age calculator
Enter a date of birth to get an exact age today, or on any date you choose, down to the day.
Date difference calculator
Enter two dates to get the number of days between them, the same span in weeks, months and years, and how many of those days are weekdays.
Fuel cost calculator
Enter the distance, your car's mpg and the local gas price to see what the drive costs, per mile and per person.
Paint coverage calculator
Enter the total length of the walls and their height to see how many gallons a room takes, with doors, windows and a second coat accounted for.
Concrete volume calculator
Enter the slab or footing size to get the concrete in cubic yards and the number of bags, so you know whether to mix it yourself or order a truck.
Recipe scaling calculator
Enter what the recipe makes and what you need, then an ingredient amount, to get the adjusted quantity in measurements you can actually use.
Tip calculator
Enter the bill, pick a tip percentage and say how many people are paying to see the tip, the total and each person's share.
Unit price calculator
Enter the price and quantity of two options in the same unit to see the price per unit for each, which one is the better deal, and the saving.
Mulch, gravel and soil calculator
Enter the bed's length, width and the depth you want, pick the material, and see the cubic yards, the number of bags, the weight and the cost either way.
Flooring calculator
Enter the room size, a waste allowance and the coverage per box to see the square feet to order, the boxes to buy and the cost.
EV vs gas cost calculator
Enter the miles you drive, the gas car's mpg and local gas price, and the EV's efficiency and your electricity rate, to see the cost per mile for each and the saving.
About these calculators
The small sums that come up all the time: what a discount actually saves, what sales tax adds in your state, how many gallons a room needs, how much concrete a slab takes, how far apart two dates are. Each calculator answers one question and shows the formula next to the number so you can check it or do it by hand next time.
Where a calculator depends on a rate that changes, like state sales tax, the rate is dated and sourced. Where it depends on a physical constant, like the volume of a US cup, the exact defined value is used rather than a rounded one.