Enter each time entry below. Add as many rows as you need.
Entry 1
h
m
Entry 2
h
m
Enter hours (0 or more).
Enter minutes (0–59).
Enter hours (0 or more).
Enter minutes (0–59).
H:MM → Decimal
Enter hours (0 or more).
Enter minutes (0–59).
Decimal → H:MM
Enter decimal hours.
e.g. 2.5 = 2h 30m
Total Time
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Sources & Methodology
Time arithmetic formulas follow the standard base-60 (sexagesimal) system used by NIST and ISO 8601.
NIST — Time and Frequency Division
National Institute of Standards and Technology — authoritative reference for time measurement and base-60 arithmetic
ISO 8601 — Date and Time Format Standard
International standard for representing dates and times, including duration arithmetic in H:MM:SS format
Methodology: Time addition converts all entries to total minutes, sums them, then divides by 60 (floor) for hours and takes the remainder for minutes. Decimal conversion: Hours + (Minutes ÷ 60). Reverse: whole number = hours, fractional part × 60 = minutes. Subtraction borrows 60 minutes from hours when needed.
⏱ Last reviewed: April 2026
How to Add and Subtract Hours and Minutes
Working with hours and minutes requires base-60 arithmetic — unlike normal addition where you carry at 10, with minutes you carry at 60. This calculator handles the conversion automatically, but understanding the math helps you verify results and work through time problems manually.
Adding Hours and Minutes
Total Minutes = (H1 x 60 + M1) + (H2 x 60 + M2) + ...
Then: Result Hours = floor(Total Minutes / 60) | Result Minutes = Total Minutes mod 60
Example: 2h 45m + 1h 30m = (2×60+45) + (1×60+30) = 165 + 90 = 255 min = 4h 15m
Example: 2h 45m + 1h 30m = (2×60+45) + (1×60+30) = 165 + 90 = 255 min = 4h 15m
Subtracting Hours and Minutes
Convert both to minutes, subtract, convert back
Convert start to total minutes, subtract end total minutes, convert result back.
Example: 5h 20m − 2h 45m = 320 − 165 = 155 min = 2h 35m
If result is negative, the subtracted time is larger than the start time.
Example: 5h 20m − 2h 45m = 320 − 165 = 155 min = 2h 35m
If result is negative, the subtracted time is larger than the start time.
Converting to Decimal Hours
Decimal Hours = Hours + (Minutes / 60)
Examples:
1h 30m = 1 + 30/60 = 1.5 hours
2h 45m = 2 + 45/60 = 2.75 hours
8h 20m = 8 + 20/60 = 8.333 hours
1h 30m = 1 + 30/60 = 1.5 hours
2h 45m = 2 + 45/60 = 2.75 hours
8h 20m = 8 + 20/60 = 8.333 hours
Converting Decimal Hours Back to H:MM
Hours = floor(Decimal) | Minutes = round((Decimal - floor(Decimal)) x 60)
Example: 3.75 hours → Hours = 3, Minutes = 0.75 × 60 = 45 → 3h 45m
Common Time Conversions Reference
| Decimal Hours | Hours & Minutes | Total Minutes | Common Use |
|---|---|---|---|
| 0.25 | 0h 15m | 15 min | Quarter hour |
| 0.5 | 0h 30m | 30 min | Half hour |
| 0.75 | 0h 45m | 45 min | Three-quarter hour |
| 1.5 | 1h 30m | 90 min | Hour and a half |
| 2.25 | 2h 15m | 135 min | Shift start rounding |
| 7.5 | 7h 30m | 450 min | Part-time workday |
| 8.0 | 8h 0m | 480 min | Full workday |
| 8.5 | 8h 30m | 510 min | Workday + lunch |
| 40.0 | 40h 0m | 2400 min | Full work week |
Why Decimal Hours Matter for Payroll
Payroll systems almost always require decimal hours, not H:MM format. If you worked 8 hours 20 minutes, you cannot multiply 8:20 × $15.00 — the math doesn't work. You must first convert to 8.333 decimal hours, then multiply: 8.333 × $15.00 = $125.00. This calculator handles that conversion instantly.
Adding Multiple Shifts for a Timesheet
When calculating weekly hours from a timesheet, use the Add Times tab and enter each shift individually. The calculator converts every entry to minutes, sums them all, and gives you the total in both H:MM format and decimal hours. For example, five 7h 30m shifts total 37 hours 30 minutes (37.5 decimal hours).
💡 Quick Rule: Every 6 minutes equals exactly 0.1 decimal hours. So 12 min = 0.2, 18 min = 0.3, 24 min = 0.4, 30 min = 0.5, 36 min = 0.6, 42 min = 0.7, 48 min = 0.8, 54 min = 0.9. This makes mental conversion much faster.
Frequently Asked Questions
Convert each time to total minutes first, add all minutes, then convert back. Add the minutes columns: if the total exceeds 59, divide by 60 and carry the whole number to hours. Example: 2h 45m + 1h 30m = 165 min + 90 min = 255 min = 4h 15m. Our calculator automates this entire process.
Divide the minutes by 60 and add that to the hours. Formula: Decimal = Hours + (Minutes / 60). Example: 2 hours 30 minutes = 2 + (30/60) = 2 + 0.5 = 2.5 decimal hours. This is the format used for payroll, billing, and most time-tracking software.
Convert both times to total minutes, subtract, then convert back. If the minutes part of the time being subtracted is larger, borrow 60 from the hours. Example: 5h 20m minus 2h 45m: convert to 320 min minus 165 min = 155 min = 2h 35m. The subtract tab on this calculator handles borrowing automatically.
1.5 hours equals 90 minutes. Multiply the decimal part by 60: 0.5 x 60 = 30 minutes, plus 1 full hour = 1 hour 30 minutes. The full 1.5 hours in minutes is 1 x 60 + 30 = 90 minutes total.
2 hours 45 minutes equals 2.75 decimal hours. Divide 45 by 60: 45/60 = 0.75. Add to hours: 2 + 0.75 = 2.75. This is commonly needed for payroll and invoicing when hourly rates are applied.
Use the Add Times tab and enter each workday as a separate time entry. The calculator sums all entries and shows the weekly total in both H:MM and decimal. For five 8-hour days it gives 40h 0m (40.0 decimal). For mixed shifts — say 7h 30m, 8h 15m, 6h 45m — it handles the minute carrying automatically.
Take the whole number as hours, multiply the decimal part by 60 to get minutes. Example: 3.75 hours: whole = 3 hours, decimal = 0.75 x 60 = 45 minutes, so 3 hours 45 minutes. Use the Convert tab to do this in either direction instantly.
150 minutes equals 2 hours and 30 minutes (2.5 decimal hours). Divide by 60: 150 / 60 = 2 remainder 30. The 2 is hours and the 30 is minutes. As a decimal: 2 + 30/60 = 2.5 hours.
Yes. Use the Add Times tab and click "Add Another Time Entry" to add as many rows as you need. This is useful for weekly timesheets, project time tracking, or totaling multiple appointments. The calculator converts all entries to minutes, sums them, and shows the combined total.
Convert both times to minutes from midnight, subtract start from end, then convert back. For example, 9:15 AM to 5:45 PM: start = 555 min, end = 1065 min, difference = 510 min = 8h 30m. Use the Subtract tab by entering the later time as the start and the earlier time as the amount to subtract.
Because time uses base 60 for minutes (and seconds), not base 10. Adding 2:45 + 1:30 as if they were decimals gives 3:75 which is wrong — there is no 75th minute. You must carry over when minutes exceed 59. This calculator handles the base-60 arithmetic automatically so you always get a correct H:MM result.
Enter each shift in the Add Times tab to get the weekly total. Note the decimal hours value shown in the results. Multiply that decimal by the hourly rate to get gross pay. Example: 42.5 decimal hours x $18.00/hr = $765.00. If your jurisdiction requires overtime, 40 regular hours x rate + 2.5 overtime hours x (1.5 x rate).
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