The rules behind the numbers

1. Hours worked

Each day: clock-out minus clock-in, minus unpaid breaks of 20 minutes or more. A clock-out earlier than the clock-in is read as a shift past midnight, and the whole shift belongs to the day it started. Minutes are counted exactly; nothing is rounded.

Short breaks are work time. Under federal rules, rest breaks of about 5 to 20 minutes are paid. Stubtally counts any unpaid break shorter than 20 minutes as worked and tells you it did. 29 CFR 785.18
Meal periods are ordinarily 30 minutes or more, with you fully relieved of work. A 20 to 29 minute unpaid break is left unpaid as you typed it, and flagged. 29 CFR 785.19
Rounding. Employers may round punches to the nearest 5, 6 or 15 minutes if, over time, it does not shortchange you. A gap of under 6 minutes is shown as possible rounding, not an error. 29 CFR 785.48(b)

2. Overtime

Federal law: at least one and a half times the regular rate for every hour over 40 in a workweek. 29 U.S.C. 207(a)(1)

A workweek is a fixed, recurring period of 168 hours (seven days in a row). Your pay period usually starts on it; set the first day of the pay period to the first day of your workweek. 29 CFR 778.105
Each workweek stands alone. In a two-week pay period, a 50-hour week has 10 overtime hours even if the other week had 30. 29 CFR 778.104

3. The regular rate

Overtime is figured from the regular rate, not just your base rate: all straight-time pay for the week (every rate you worked at, shift differentials, and bonuses you were promised for work, attendance or production) divided by all hours worked. Each overtime hour then adds half of that rate on top of the straight time already counted. 29 CFR 778.107-778.115, 778.207(b), 778.208

Gifts, discretionary bonuses, holiday and vacation pay and expense reimbursements are not part of the regular rate. Put them in “Other pay”: they are added to both sides of the comparison as they are. 29 CFR 778.211, 778.217-778.219

4. State presets

Every preset keeps the federal 40-hour weekly rule. Hours already paid as daily overtime are not counted again toward the 40.

Preset	Daily overtime	Source
Federal	none	29 U.S.C. 207(a)(1); 29 CFR 778.104, 778.105
California	1.5x over 8 hours in a workday; 2x over 12. On the 7th day in a row worked in one workweek: 1.5x for the first 8 hours, 2x after.	California Labor Code 510(a)
Alaska	1.5x over 8 hours a day (employers of 4 or more employees)	Alaska Statutes 23.10.060
Colorado	1.5x over 12 hours in a workday (the separate “12 consecutive hours” rule is not modelled)	Colorado COMPS Order, 7 CCR 1103-1, Rule 4.1.1
Custom	1.5x over the daily limit you type	your own

Other states may have overtime, meal-break or minimum-wage rules beyond these. Check with your state labor office.

5. Worked example

The sample week on the home page: $18.00 an hour, federal rule. The Wednesday line has a 30-minute lunch and a 15-minute break, both taken off as unpaid.

Hours worked (the 15 minutes count): 48 h
Straight time / overtime: 40 h / 8 h
Pay at straight time: 48 h × $18.00: $864.00
Regular rate: $864.00 ÷ 48 h: $18.00/h
Overtime premium: 8 h × half of the regular rate: $72.00
Gross by the times: $936.00
The stub (47.75 h paid): $929.25

6. What Stubtally does not cover

Salaried and exempt jobs, tips and tip credits, piece rates, commission-only pay.
Taxes, deductions and net pay: it checks gross pay only.
California’s separate formula for flat-sum bonuses, meal and rest-break premium pay, split-shift and reporting-time pay.
State minimum wages (it checks only the federal $7.25 an hour, on each workweek’s straight-time pay divided by the hours worked; 29 U.S.C. 206(a)(1)(C)).
Whether your job is covered by the overtime law at all. Most hourly jobs are; some are not.

Questions about the law: U.S. Department of Labor, Wage and Hour Division, 1-866-487-9243 (dol.gov/agencies/whd), or your state labor office. Stubtally is a calculator, not legal advice.