Hours calculator

7 h 45 min → 45 ÷ 60 = 0.75 → 7.75 hours

Why 6.40 + 7.35 + 5.50 on a calculator is wrong

Hours and minutes don't add like decimals, because the minutes carry over at 60, not at 100. Type three days of 6:40, 7:35 and 5:50 into a pocket calculator as 6.40 + 7.35 + 5.50 and it says 19.25. The real total:

hours:   6 + 7 + 5      = 18
minutes: 40 + 35 + 50   = 125 = 2 h 05 min
total:   20:05          = 20.08 hours

Read as hours, 19.25 is 19 hours 15 minutes, which is 50 minutes short of the time actually worked.

Convert the total once

Rounding each entry to two decimals and then adding drifts. Three 20-minute calls are 0.33 + 0.33 + 0.33 = 0.99 hours, but together they are exactly one hour. Add the minutes first, then divide by 60 once. The calculator works that way.

Billing increments: what they add, per entry or on the total

A billing increment means time is billed in fixed steps, say 15 minutes, so a 3:20 session goes on the invoice as 3:30. Whether you round each entry or only the total makes a real difference. The example in the calculator has four entries:

3:20 + 4:20 + 2:45 + 2:15 = 12:40 = 12.67 hours

With a 15-minute increment, rounded up:

• Per entry: 3:30 + 4:30 + 2:45 + 2:15 = 13:00, 20 minutes more. At $85 an hour that is $1,105.00 instead of $1,076.67.
• Once on the total: 12:40 becomes 12:45, 5 minutes more, $1,083.75.

Rounding up per entry can add up to 14 minutes to every entry, so many short entries add up fast. Rounding to the nearest step instead can go either way: per entry, the same four come to 12:30, ten minutes less than the time worked.

Thomas Kraaibeek, who builds CronLoom, rounds his own entries to the nearest quarter hour. An invoice line then reads 1, 1.25, 1.5 or 1.75 hours instead of an odd decimal like 1.38. Some entries go up and some go down, and in his experience it evens out.

For employees in the US, the Department of Labor accepts time clocks that round to the nearest 5 minutes or to the nearest tenth or quarter of an hour, as long as the rounding averages out so people are paid for all the time they actually work (29 CFR 785.48(b)). For a freelancer, the increment is a term of the contract, not a law. Write it into the agreement, and round the way it says.

Breaks and hours past midnight

The break on an entry is taken off that entry: 13:05 to 17:40 with a 15-minute break is 4:20. If an entry ends earlier than it starts, the calculator reads it as running past midnight, so 22:30 to 0:45 is 2:15.

Totals are where the work starts. The more useful question is what each of those hours earned once the unbilled ones are counted. The effective hourly rate calculator answers it, and billable vs non-billable hours explains which hours to count. In CronLoom the totals keep themselves as you track, and an entry can be rounded up or down to the quarter hour when you edit it.