THE NUMBERS, EXPLAINED
How to use this calculator.
Uses standard GBP coin and note denominations, rounding both entered amounts to pennies.
Start with your inputs
Enter price (£), cash paid (£). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Price (£) | 7.35 |
| Cash paid (£) | 10 |
A worked example
With the example inputs above, change due (£) is 2.65. Change the inputs to explore your own scenario.
Putting the example numbers into the formula
Change due (£)
round(((10)-(7.35)) × 100) ÷ 100 = 2.65
| Result | Example answer |
|---|---|
| Change due (£) | 2.65 |
| GBP denominations | 1 × £2.00; 1 × £0.50; 1 × £0.10; 1 × £0.05 |
How this is calculated
Change due (£)
round((b-a) × 100) ÷ 100
GBP denominations
GBPchange(a,b)
Symbols and units
- a
- Price (£)
- b
- Cash paid (£)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Calculation steps and notation
round(x) rounds to the nearest integer, with exact halfway ties towards positive infinity.
Round the price and payment separately to pennies and subtract them. Starting with £50, use as many of each denomination as fit, then continue through £20, £10, £5, £2, £1, 50p, 20p, 10p, 5p, 2p and 1p. The separately displayed change amount rounds the difference to pennies; use penny-precision inputs to avoid different rounding conventions.
Assumptions and limits
Uses standard GBP coin and note denominations, rounding both entered amounts to pennies.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Change due (£); GBP denominations. The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Uses standard GBP coin and note denominations, rounding both entered amounts to pennies.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Further reading
Background reading; this does not imply endorsement or independent review of SumFizz.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →