Home & Everyday Calculators
7 free home & everyday calculators, each explaining its formula.
Practical calculations for the house, the car, the kitchen and the shop — quantities, costs and the comparisons that save money.
Fuel Cost Calculator
The number that makes a long commute feel real, and the one people forget when comparing two cars.…
Home & EverydayElectricity Cost Calculator
Wattage times hours times tariff. The surprise is usually which appliances turn out to matter and which do not.…
Home & EverydayPaint Calculator
Buying one tin short halfway through a wall is worse than buying one too many — colour batches vary.…
Home & EverydayUnit Price Comparison
The bigger pack is usually cheaper per unit. Usually — and supermarkets rely on you assuming it always is.…
Home & EverydayGPA Calculator
A GPA is a credit-weighted average, which means a four-credit course counts twice as much as a two-credit one.…
Home & EverydayTile Calculator
The wastage allowance is the part people skip, and it is the reason so many tiling jobs stop one box short.…
Home & EverydayConcrete Calculator
Concrete is ordered in cubic metres and sold in 20 kg bags, and the conversion between them surprises people every time.…
About this section
These are the calculations that decide how much material to order, what something actually costs to run, and whether the larger pack is genuinely better value. They are unglamorous and they are where a surprising amount of household money is decided.
Two themes run through this section. The first is that quantities need a wastage allowance, and the allowance is not optional. Tiles break, cuts produce offcuts that fit nowhere else, and paint soaks into textured surfaces faster than the tin predicts. Running out with one wall left is worse than over-ordering, because production batches vary in colour.
The second is that running costs are dominated by heat. Anything that generates or moves heat — showers, heaters, tumble dryers, kettles, fridges — accounts for the overwhelming share of a typical electricity bill, while the electronics people worry about are usually trivial by comparison. Knowing which is which is worth more than any amount of unplugging chargers.
Every page states the formula, shows a worked example with realistic figures, and lists the costs the calculation does not include — adhesive and grout alongside tiles, transaction costs alongside fuel, maintenance alongside a monthly payment.