摘要
Splitting a bill means dividing a shared expense — typically a restaurant meal — among the people who participated. There are several fair ways to do this, from simple equal division to more nuanced methods based on what each person ordered or earned. The calculator supports four methods: equal, custom percentage, itemised, and income-based splitting.
工作原理
Tip calculation
The tip (or service charge) is always calculated on the subtotal — the bill amount before tip is added:
Where
The grand total is then subtotal + tip.
Method 1: Equal split
Everyone pays the same amount. The grand total is divided evenly, with any remainder pennies distributed one-per-person to avoid rounding errors.
Where
Method 2: Custom percentage split
Each person pays a set percentage of the total. Useful for couples who want a 60/40 or 70/30 split. The percentages must add up to 100%.
Where
Method 3: Itemised split
Each person pays for what they ordered. Communal items (shared starters, a bottle of wine) are divided equally. The tip is then distributed proportionally — the person who ordered more pays a proportionally larger share of the tip.
Where
Method 4: Income-based split
The bill is divided proportionally to each person’s annual income. This is popular among couples or housemates with significantly different salaries — the higher earner pays a larger share.
Where
Worked examples
Equal split: £85 dinner, 4 people, 12.5% tip
Equal split: £85 bill, 4 people, 12.5% service charge
Calculate tip
= £10.63
Grand total
= £95.63
Per person
= £23.91 / £23.90
Result
Each person pays approximately £23.91
Income-based split: £80 dinner, £45k / £15k salaries, 10% tip
Income-based split: £80 bill, incomes £45k and £15k, 10% tip
Calculate tip
= £8.00
Grand total
= £88.00
Income ratio
= 75% / 25%
Person A (£45k) pays
= £66.00
Person B (£15k) pays
= £22.00
Result
Higher earner pays £66.00, lower earner pays £22.00
UK tipping etiquette
- 12.5% is the traditional discretionary service charge in UK restaurants, especially in London.
- 10% is common outside London and considered the minimum for good service.
- 15% is becoming more common in upscale London restaurants (as of 2025).
- Service charges are discretionary — you can ask for them to be removed.
- Since October 2024, the Employment (Allocation of Tips) Act requires employers to pass 100% of tips and service charges to workers.
- Always check whether a service charge is already on your bill before tipping extra.
Rounding
When a total doesn’t divide evenly, penny remainders must go somewhere. This calculator uses the largest-remainder method: it gives each person the rounded-down amount, then distributes the leftover pennies one at a time to those who lost the most to rounding. This ensures the shares always sum exactly to the grand total.
假设与局限
- All calculations are in pence (integers) for precision. Amounts are converted to pounds for display only.
- Tip is calculated on the subtotal (pre-tip amount), not on a total that already includes service charge.
- The income-based method uses gross annual salary as the basis for proportional splitting. It does not account for tax, student loan repayments, or other deductions.
- Itemised mode ignores the bill total slider — it calculates the subtotal from the items entered.
验证
| Test case | Input | Expected | Source |
|---|---|---|---|
| Equal, clean division | £120, 3 ppl, 10% tip | £44.00 each | Manual calculation |
| Equal, rounding needed | £85, 4 ppl, 12.5% tip | £23.91/£23.90 | Manual calculation |
| Percentage 60/40 | £100, 10% tip | £66.00 / £44.00 | Manual calculation |
| Income 75/25 | £80, 10% tip, £45k/£15k | £66.00 / £22.00 | Manual calculation |
| Itemised with shared | Alice (£15+£8), Bob (£22), shared £6, 10% tip | A: £28.60, B: £27.50 | Manual calculation |