Numbers and rounding
- Money is rounded to the cent, with halves rounded up. 2.675 becomes 2.68. Rounding uses a decimal-safe method, so binary floating-point artifacts (such as 1.005 appearing as 1.00) do not change results.
- Time is kept in whole minutes. Hours and minutes are added as minutes and converted to decimals only at the end, which avoids rounding drift. Decimal hours are rounded half up at two places unless you choose more.
- Percentages and ratios are calculated at full precision and shown to up to six decimal places, with trailing zeros removed.
- Each page says where it rounds. If rounding could matter, the steps show the unrounded value first.
Validation: no silent fixes
A calculator never replaces a bad entry with a guess. Text where a number belongs, negative numbers where they make no sense, impossible dates (such as February 30) and division by zero produce a message beside the field. A blank required field shows an empty state. Results never display NaN or infinity.
Time and date rules
- Clock times are 24-hour wall-clock times in one time zone. An end earlier than the start is read as the next day. Equal times are zero.
- Calendar dates use the Gregorian calendar, including leap years (divisible by 4, except century years not divisible by 400). Date arithmetic works on calendar days, so time zones and daylight saving time do not affect it.
- Months are counted by stepping from the start date. If the day does not exist in the target month, the last day of that month is used (January 31 plus one month is February 28 or 29).
- The time duration calculator is the one tool that uses real elapsed time. With dates entered, it uses your device's time zone and warns when daylight saving time changes the elapsed hours.
Work and pay rules
- Overtime follows the federal Fair Labor Standards Act: 1.5 times the regular rate for hours over 40 in a fixed seven-day workweek, calculated one week at a time. Weeks are never averaged. State daily overtime rules are not calculated.
- Regular rate with a bonus follows the Department of Labor method: total straight-time pay for the week including non-discretionary bonuses, divided by hours worked. Only the extra half-time premium is added on overtime hours.
- Time rounding to 5, 6 or 15 minutes follows 29 CFR 785.48 options and rounds each punch to the nearest step, with halves rounded up (7 minutes down, 8 minutes up for 15-minute steps).
- Pay conversions default to 40 hours a week for 52 weeks (2,080 hours), and you can change both.
- Pay results are gross and exclude taxes and deductions.
Holidays and business days
US federal holidays are generated from the rules in 5 U.S.C. 6103 for 2021 through 2040, with Saturday holidays observed on Friday and Sunday holidays observed on Monday. They are checked against published Office of Personnel Management lists. Outside that range, only weekends are skipped, and the tool says so.
What we test
Every calculator has automated tests with answers worked out independently. They cover normal values, zero, negatives, decimals, very large values, blank and invalid input, rounding boundaries, leap days, daylight saving time changes, overnight shifts, break deductions and currency precision. The tests run before every release. We also run the site in real browsers at phone, tablet and desktop widths to confirm that the page and the engine agree.
Privacy of calculations
All math runs in your browser. Inputs are not transmitted. See the privacy policy.
Spot an error?
Please tell us. Corrections are described in the editorial standards.