Guides to working out your costs

Learn how to work it out yourself and how to read every result.

How to calculate an appliance’s electricity use and cost

The watts-to-kWh-to-cost formula explained with examples, and why rated power is not always real consumption.

Measure walls, subtract openings, apply coats and coverage: the full method to buy the right amount of paint.

The formula in L/100 km and mpg, how to convert between them and what makes real consumption differ from official figures.

What total cost of ownership means, which items to include and how to work out how many years an EV takes to pay off.

How to calculate price per kilo, pound or litre, convert units and avoid common packaging and offer traps.

Steps to build a realistic budget, how to classify spending, and what the 50/30/20 rule actually is — and its limits.

Equal or income-proportional splits, how to work out balances and how to settle up with the fewest transfers.

The formulas to work out time to your goal or the monthly contribution needed, with examples and no promises of returns.