Everyday
Time Calculator
Add and subtract time without base-60 mistakes. Enter two durations in hours and minutes, choose add or subtract, and get the result as hours-and-minutes, decimal hours (for timesheets), total minutes, and days.
Result
10h 15m
Decimal hours
10.25
Total minutes
615
In days
0.427
Time math is base-60: 7h 45m + 2h 30m is 10h 15m, not 10.75 + — this is exactly the mistake decimal calculators make. Decimal hours shown here are minutes ÷ 60, the format timesheets expect.
How it works
Time is base-60, which is why ordinary calculators get it wrong: punching in 7.45 + 2.30 gives 9.75, but 7h 45m + 2h 30m is actually 10h 15m. The digits after the decimal point aren't minutes.
The reliable method is to convert everything to minutes first: 7h 45m is 465 minutes, 2h 30m is 150. Add them (615), then convert back — 615 ÷ 60 = 10 remainder 15, so 10h 15m.
Decimal hours are a different beast entirely: they're minutes divided by 60, so 45 minutes is 0.75 hours. Payroll and billing systems want this format, and the calculator shows it alongside the h:mm result so you never mix the two up.
total minutes = (h₁ × 60 + m₁) ± (h₂ × 60 + m₂)
hours = total ÷ 60 (whole part), minutes = remainder
decimal = total ÷ 60
Example: 7h 45m + 2h 30m = 465 + 150 = 615 min = 10h 15m = 10.25 hrsFrequently asked questions
Why can't I just add times on a normal calculator?
Because normal calculators work in base-10 while time is base-60. Entering 1.50 for an hour and a half happens to work (1h 30m = 1.5), but 1.45 for 1h 45m doesn't — that's actually 1h 27m in decimal. Convert to minutes first, or use this tool.
How do I convert minutes to decimal hours?
Divide by 60. 15 minutes = 0.25 hours, 20 = 0.33, 45 = 0.75. Going the other way, multiply the decimal part by 60: 3.4 hours = 3 hours + 0.4 × 60 = 3h 24m.
What does a negative result mean?
You subtracted a longer duration from a shorter one — the result is shown with a minus sign. Useful for 'how far behind schedule am I' style questions.
Can I add more than two durations?
Chain the calculations: add the first two, then add the next duration to the result. For timesheets, a quicker route is converting each entry to decimal hours and summing those.
How do I add time to a clock time, like 9:40 + 2h 45m?
Same math with a wrap-around: 9:40 is 580 minutes past midnight, plus 165 minutes is 745 = 12:25. If a sum passes 1440 minutes, subtract 1440 — you've crossed midnight into the next day.