Everyday Calculators
Bills, fuel, energy and shopping
What things actually cost to run
Running costs are unintuitive because they are small numbers multiplied by large ones. An appliance drawing 100 watts sounds trivial until it runs continuously for a year and consumes 876 kilowatt-hours. The electricity cost calculator does that multiplication for you at your own tariff, per day, per month and per year, which is usually enough to reorder your assumptions about which appliances matter.
Fuel works the same way. The fuel cost calculator handles the four common ways of expressing economy — miles per gallon in both US and imperial gallons, litres per 100 km, and kilometres per litre — because a car bought in one market and driven in another will have its economy quoted in a unit the driver does not think in.
Bigger decisions, same arithmetic
Solar sizing is the same calculation extended over years: system size against expected output against tariff, resolved into a payback period. The result depends heavily on assumptions about sunlight hours and future electricity prices, so the calculator shows what it assumed rather than presenting a single confident figure.
The speed, distance and time calculator solves for whichever of the three you are missing, in whichever units you are thinking in. It is the most-used tool in this category because journey planning is the one piece of arithmetic almost everyone does regularly, and because doing it in your head is exactly hard enough to get wrong.
As everywhere on this site, these run in your browser: your tariff, your mileage and your travel plans are not sent anywhere.
Everyday calculators — common questions
How do I work out what an appliance costs me?
You need its power draw in watts, roughly how many hours a day it runs, and your electricity rate per kilowatt-hour — the rate is on your bill and the wattage is on the appliance’s label or in its manual. The electricity cost calculator turns those three into a daily, monthly and annual cost. For anything with a thermostat, use average running hours rather than the hours it is switched on.
Which fuel economy unit should I use?
Whichever your car reports, then convert once. Miles per gallon and kilometres per litre get better as the number rises; litres per 100 km gets better as it falls, which is why the two families are so easy to confuse. The fuel cost calculator accepts all of them and converts between them, so you never have to hold two conventions in your head at the same time.
Is the solar payback period reliable?
It is a reasonable estimate under stated assumptions and no more than that. Actual output depends on your latitude, roof angle, shading and local weather, and payback depends on electricity prices over a period of years that nobody can forecast. Treat it as a way to compare options against each other rather than as a prediction of a date.
Do these use my location or my currency?
Only what you type. The tools take a rate and a currency from you rather than looking anything up, so they work identically in any country. No location is requested, and nothing you enter leaves your browser.