Calculating Change Correctly (Two Simple Methods)

Working out change is one of the most useful bits of maths a child ever learns, because they'll use it for the rest of their life, often without a calculator in reach. There are two solid ways to do it, and it's worth knowing both.

Method one: straightforward subtraction

The most direct method is subtracting the price from the amount paid. An item costs £3.65, and you pay with a £5 note: £5.00 − £3.65 = £1.35 change.

Method two: counting up

Counting up starts at the price and adds small amounts until reaching the amount paid, which is often how it's done at a real till. From £3.65, add 5p to reach £3.70, then 30p to reach £4.00, then £1.00 to reach £5.00. Adding those jumps together — 5p + 30p + £1.00 — gives £1.35, exactly matching the subtraction method.

Real-life example: buying a drink

A drink costs £2.30, and a snack costs £1.45. Together they cost £2.30 + £1.45 = £3.75. Paying with a £5 note, the change is £5.00 − £3.75 = £1.25.

Real-life example: paying with a £20 note

An item costs £12.45, paid for with a £20 note. The change is £20.00 − £12.45 = £7.55.

Practice questions

• Item costs £4.30, paid with £5. Change? Answer: £0.70
• Item costs £8.75, paid with £10. Change? Answer: £1.25
• Item costs £15.60, paid with £20. Change? Answer: £4.40
• Two items cost £3.20 and £2.10, paid with £10. Change? Answer: £4.70
• Item costs £0.60, paid with a £1 coin. Change? Answer: £0.40

Common mistakes I see in the classroom

The most common one is misaligning the decimal point when subtracting pounds and pence, especially when the price has two decimal places and the payment doesn't, like subtracting £3.65 from £5 as if it were £5.00 written as just "5."

Another frequent mistake happens with multiple items — forgetting to add all the item prices together first, before working out the change from the total, and instead subtracting just one item's price by accident.

Tips for parents

Let your child work out the change before the cashier's screen shows it, using real prices at a real till. It's low-pressure, genuinely useful practice that happens naturally during an ordinary errand.

Tips for teachers

I teach counting up alongside subtraction, not instead of it, since some students find one method click faster than the other. Letting a class try both on the same question, then compare answers, shows that either path leads to the same correct change.

How step-by-step learning tools help

A step-by-step maths tool can show both the subtraction method and the counting-up method side by side for the same question, with unlimited fresh change calculations for a child to practise at their own pace.

Frequently asked questions

What's the easiest way to calculate change? Subtracting the price from the amount paid is the most direct method, though counting up in small steps can feel quicker and more natural without a written sum.

Why does counting up work as well as subtraction? Because adding small jumps from the price up to the amount paid covers exactly the same gap that subtraction measures directly — both methods describe the same distance between two numbers.

At what age do children learn to calculate change? Simple change with whole pounds usually starts around age 6 to 7, with pounds and pence together following from age 8 to 9.

How do you calculate change for more than one item? Add all the item prices together first to find the total cost, then subtract that total from the amount paid.

What's a good way to check a change calculation? Add the change back to the price — if it equals the amount paid, the change is correct.

Two Paths, Same Answer

Whether a child reaches for subtraction or counting up, calculating change correctly comes down to trusting the gap between two numbers. Once either method feels secure, working out change at any till becomes second nature.