Formulas and sources
Each formula this calculator uses, where it comes from, and what it leaves out. "How it works" shows the same formula with your own numbers.
Tip amount
Simple, Dining and Split modes, on the bill before tax
- T
- the tip
- B
- the bill, before tax
- P
- the tip percentage
Simple and Split modes always tip on the bill. Dining mode starts there too, and can switch the base.
Source: Standard formula; no single publisher.
Tip on the bill with tax
Dining mode, with the Post-Tax base
- T
- the tip
- (B + Tax)
- the bill plus the tax you enter
- P
- the tip percentage
Source: Standard formula; no single publisher.
Tip on an amount you enter
Dining mode, with the Custom Base
- T
- the tip
- Custom base
- the amount you choose to tip on
- P
- the tip percentage
Source: Standard formula; no single publisher.
Total
Every mode
- Total
- what the table pays
- B
- the bill
- Tax
- the tax you enter, in Dining mode
- T
- the tip
- Service Charge
- a charge the venue adds, counted only when it is not already in the bill entered
Under US federal wage rules, a compulsory service charge is not a tip.
Source: Standard formula; no single publisher. Service charge and tip: 29 CFR 531.55(a) [1].
Equal split
Simple, Dining and Split modes, for an equal split
- Per person
- each person's share
- N
- the number of people paying
The whole bill is split, tip included; the tip is not divided among staff. When equal shares in whole cents miss the total, a note says so.
Source: Standard formula; no single publisher.
Weighted split
Split mode, for a weighted split
- Each share
- one person's share
- weight
- the weight you give that person
Each person's weight sets their part of the whole bill, tip and tax included.
Source: Standard formula; no single publisher.
Starting tip percentage by region
Every mode
A region sets a starting percentage and four quick picks, on the bill before tax.
Source: CalcTrail's own starting points; no publisher. Official tourism, government or consumer pages back part of the note for 17 of the 23 regions, and India's rule comes from consumer-protection guidelines the Delhi High Court upheld on March 28, 2025 [2]. For the other 5, no primary source was found. No US law sets a tip percentage; the federal minimum cash wage for a tipped worker is $2.13 an hour [3].
Sources
- U.S. Department of Labor, Wage and Hour Division. 29 CFR 531.55: Examples of amounts not received as tips, paragraph (a). eCFR, current as of October 1, 2026.
- Press Information Bureau, Government of India (Ministry of Consumer Affairs). Press release on the CCPA action against restaurants levying a default service charge (PRID 2213227), the Delhi High Court judgment of March 28, 2025, and the CCPA guidelines of July 4, 2022. January 10, 2026.
- U.S. Department of Labor, Wage and Hour Division. 29 CFR 531.50: Statutory provisions with respect to tipped employees, paragraph (a). eCFR, current as of October 1, 2026.
What this calculator does not cover
- It does not know any venue's service charge, tax or tipping rule.
- Round Total and Round Per Person raise the tip percentage until the total, or each share, reaches the next whole amount. That rounding is CalcTrail's own.
- Tax, a service charge and another tip base count only in Dining mode.
Sources checked on .