Nobody wants to sit at a restaurant doing long division while the check sits in the middle of the table. Most tip-and-split conversations get tense precisely because the arithmetic ends up happening late, from memory, under pressure. The fix takes three numbers — the subtotal, the tip percent, and the headcount — and ordering the steps so they stay small.

Start with the subtotal, not the total

The tip is conventionally calculated on the pre-tax subtotal — service isn’t taxed, so the tip isn’t either. That’s the number printed right under the itemized list on most checks.

tip = subtotal × (percent ÷ 100)
final = subtotal × (1 + percent ÷ 100)

Example: subtotal $86.00, tip 18%:

tip = 86 × 0.18 = $15.48
total = 86 × 1.18 = $101.48

If you’d rather tip on the total, run the tip calculator with the other base and see the difference — typically a few dollars, though the convention at most tables is the subtotal.

Tip percentages that keep the math easy

Common US benchmarks: 15% standard, 18–20% for good service, 10% for poor service. Whatever you pick, anchor everything to 10%:

  • 10% → shift the decimal: 86 → 8.60.
  • 20% → double the 10%: 17.20.
  • 15% → 10% plus half of that: 8.60 + 4.30 = 12.90.
  • 18% → 20% minus 2% (one-fifth of 10%): 17.20 − 3.44 = 13.76.
  • 25% → double 10% plus half of 10%: 17.20 + 4.30 = 21.50.

Rounding to the dollar is normal: on $86, a 15% tip comes to about $13.

Splitting the check: the fair way

For an equal split of one check, start from an even share:

even_share = total ÷ n

Then nudge it for anyone who ordered extras (drinks, appetizers). The method that matches how groups actually think:

  1. Add up each person’s extras.
  2. Subtract extras from the bill.
  3. Divide the remainder evenly.
  4. Give each person their extras back.
person_share = (total − total_extras) ÷ n + own_extras

Distribute the tip on top proportionally — or have one person pick up the tip and the rest split the food cost. An item-by-item proportional split is the most “fair,” but rarely worth the added confusion at the table. An even split with extras added on is accurate enough for any group.

When the group isn’t equal

Three people share a pitcher of sangria; two don’t drink. Now the even split is wrong. The item-based split handles it: total each person’s own orders, divide shared items among those who shared them, then add tax and tip proportionally:

total_share = (own_items + (shared_items ÷ sharers) + tax_share) × (1 + tip%)

The tip calculator handles the numbers instantly; the split bill calculator does the whole dance.

When gratuity is already included

Many restaurants add automatic gratuity to large parties (commonly 15–18% for groups of 6+), and delivery apps add a fixed service fee. Once a gratuity is on the bill, don’t double-tip:

  • Check the line that says “18% gratuity” or “service charge” near the bottom.
  • If the tip is included, leave $0 extra (or a few dollars for genuinely great service).
  • If a service fee replaces the tip (common with a kitchen fee or delivered order), the server may not get it — a small cash tip is appreciated when the service was good.

FAQ

How do I calculate a tip without a calculator? Find 10% by shifting the decimal; 20% is double; 15% is 10% plus half; 25% is double 10% plus half a 10%. Round to a whole dollar when table math matters more.

What tip percentage is standard? 15% is the baseline, 18–20% for good service, 25% for exceptional. Dine naturally adjusts by city and venue; 20% is safe nearly anywhere in the US.

Tip on the before-tax or after-tax amount? Before tax. Tips go to service, and service isn’t taxed. Tipping on the tax-inflated total just raises the tip by a few dollars.

What’s the formula for splitting an unequal table? Lowest common denominator: each person pays their itemized subtotal plus their share of shared dishes, with tax and tip scaled to the individual subtotal. The split bill calculator does exactly that.

Do I double-tip when gratuity is included? No. An “18% gratuity” line for large parties is the tip — skip adding your own. A “service charge” isn’t the tip at all; if you want the server to get money, hand it over in cash.