How to Calculate a Tip: The Simple Formula Every Diner Needs
Figure out exactly what to leave in seconds with the Tip Calculator, or keep reading to understand the math yourself.
Tipping is one of those small social calculations that can feel surprisingly high-stakes at the end of a meal. You're tired, the bill has tax on it, and three people at the table have different opinions on what's fair. Here is everything you need to know to get it right every time — no smartphone required.
The Standard Tip Tiers
The restaurant industry generally recognizes three baseline tiers:
- 15% — Adequate service, no major issues
- 18% — Good service, the common baseline in many cities
- 20% — Great service, the modern standard most servers expect
Some diners default to 15% out of habit, but the cost-of-living reality for tipped workers has shifted the social expectation upward. Most financial etiquette guides now treat 20% as the floor for competent service, with 25% or more for exceptional experiences.
The Move-the-Decimal Trick for 20%
Forget complex math. Here is the fastest mental method for calculating a 20% tip:
- Look at your bill total.
- Move the decimal point one place to the left — this gives you 10%.
- Double that number — this gives you 20%.
Example: Your bill is $47.00.
- Move the decimal: $4.70 (this is 10%)
- Double it: $9.40 (this is 20%)
For 15%, take your 10% figure and add half of it: $4.70 + $2.35 = $7.05.
For 18%, use the 20% amount and subtract roughly 10% of the tip itself — it gets you close enough without doing long division at the table.
Pre-Tax vs Post-Tax: Which Number Do You Tip On?
This is a genuine debate, and the short answer is: either is acceptable, but tipping on the pre-tax subtotal is technically more precise.
The tax portion of your bill is money that goes directly to the government — your server never sees it. Tipping on the pre-tax amount means you are tipping on what you actually paid for the service and food.
That said, the dollar difference is usually small. On a $50 meal with 8% sales tax, your post-tax total is $54. The difference between tipping 20% on $50 ($10.00) versus 20% on $54 ($10.80) is 80 cents. Most people tip on the post-tax total simply because that is the final number printed on the check.
Splitting a Group Bill: A Worked Example
Here is a real scenario. You and two friends finish dinner. The bill is $73.50 before tax. You want to tip 20% and split everything three ways.
Step 1 — Calculate the tip:
- Move the decimal: $7.35 (10%)
- Double it: $14.70 (20%)
Step 2 — Calculate the total:
- $73.50 + $14.70 = $88.20
Step 3 — Split three ways:
- $88.20 ÷ 3 = $29.40 per person
If you want to round up to the nearest dollar for simplicity, each person pays $30, which leaves a tip of $16.50 — slightly above 22%. Most servers will not complain.
A word on group dynamics: if one person at the table ordered significantly more than others, a flat even split can cause friction. In those cases, it is fairer to split the food costs by what each person ordered, then split the tip evenly on the total — since the server served everyone equally.
When to Tip More (or Less)
Most guides focus on the standard tiers, but a few situations call for adjustment:
Tip more when:
- The restaurant is clearly short-staffed and your server is handling extra tables
- You stayed at the table significantly longer than a normal meal duration
- You made complex modifications or had large requests
- The service genuinely impressed you
Tip less (but still tip something) when:
- The service was slow due to something clearly in the server's control, like long stretches without check-ins on a slow night
- Order errors happened and were not addressed
Note on buffets and counter service: Tipping is generally not expected at full buffets where no table service is provided, or at counter-service restaurants where you order at a register. The social contract is different when there is no table attendant.
Skip the math entirely — the Tip Calculator handles the split, the percentage, and the per-person total in one step.