Convert times to minutes, find each line's length, subtract breaks, then add
Add 9:00 AM – 12:00 PM and 1:00 PM – 6:00 PM and you get 3 hours plus 5 hours, which is 8 hours. With more lines it gets hard to do in your head, so every time is turned into minutes since midnight. A line whose end is earlier than its start is treated as ending the next day (1,440 minutes are added), and any break is taken off that line. Finally the remaining time of each line is added up and written again as hours and minutes.
The calculator opens with a sample work week. Monday and Tuesday run 9:00 AM – 6:00 PM less a 1-hour break, so 8 hours each. Wednesday runs 9:00 AM – 8:00 PM less 1 hour, so 10 hours. Thursday, 2:00 PM – 5:30 PM, is 3 h 30 min. Friday starts at 10:00 PM and ends at 7:00 AM the next day, 8 hours after the break. Saturday has no clock times, only a length of 1 h 30 min. Together that is 39 hours, or 2,340 minutes, or 39.00 hours as a decimal. The breaks removed come to 4 hours, so the time including breaks is 43 hours. On the scale bar the pieces of each line sit end to end and stop just short of the 40-hour goal mark.
When you need to add several intervals
Time is rarely logged as one block. These are the usual cases where you need the sum of the pieces. The rules quoted here are the US federal Fair Labor Standards Act (FLSA) only.
- Checking a work week against 40 hours: under the FLSA, covered employees must receive overtime pay for hours worked in excess of 40 in a workweek (29 U.S.C. 207(a)(1); DOL Fact Sheet #23). Enter clock-in and clock-out times plus unpaid meal periods and the goal line shows how close the week is to 40.
- Checking an hourly paycheck: pay for hourly work follows hours worked, so compare the hours on your pay stub with your own total before anything else.
- Tracking study or project time by label: type a subject or project name in the label box and lines with the same name are grouped into a subtotal and a share of the total. For videos or lectures where you only know the length, add a length line.
- Billing by the hour: freelance, consulting and tutoring invoices often want 1 h 30 min written as 1.50 hours. The decimal hours under the total are that number.
- Adding meeting, call or video lengths: lengths such as 1 h 45 min and 2 h 20 min can be entered as hours and minutes and added directly.
How it is calculated
- Turn each time into minutes. 9:30 AM is 9 × 60 + 30 = 570 minutes, and 6:00 PM (18:00) is 1,080 minutes.
- Find the length of the line. Subtract the start from the end: 1,080 − 570 = 510 minutes for 9:30 AM – 6:00 PM.
- If the end is earlier than the start, add one day. 10:00 PM – 7:00 AM is 420 + 1,440 − 1,320 = 540 minutes, or 9 hours. When start and end are identical it cannot tell 0 minutes from 24 hours, so it counts a full day only if you press “Count as 24 h”.
- Subtract the break. 540 minutes minus a 60-minute break leaves 480 minutes. A break as long as the line, or longer, is an input mistake, so that line is left out.
- Add every line and split again. Total minutes divided by 60 gives the whole hours, the remainder is the minutes, and decimal hours are total minutes ÷ 60.
Line time = (end − start, + 1,440 if the end is earlier) − break · Total = Σ line times · Decimal hours = total minutes ÷ 60
A length line is hours × 60 + minutes. If you fill in only one box, the other counts as 0, and 90 in the minutes box is added as 1 h 30 min.
A sample work week
This is the same log the calculator opens with. The running total adds the line times from the top down and matches where each piece ends on the scale bar.
| Day | In – out | Break | Hours worked | Running total |
|---|---|---|---|---|
| Mon | 9:00 AM – 6:00 PM | 1 h | 8 h | 8 h |
| Tue | 9:00 AM – 6:00 PM | 1 h | 8 h | 16 h |
| Wed | 9:00 AM – 8:00 PM | 1 h | 10 h | 26 h |
| Thu | 2:00 PM – 5:30 PM | None | 3 h 30 min | 29 h 30 min |
| Fri | 10:00 PM – 7:00 AM (next day) | 1 h | 8 h | 37 h 30 min |
| Sat | Length 1 h 30 min | — | 1 h 30 min | 39 h |
| Total | 4 h | 39 h | Try it in the calculator |
The week totals 39 hours, under the 40-hour line the federal overtime rule uses. The FLSA overtime rule counts hours over 40 in a workweek, so a 10-hour Wednesday does not by itself trigger federal overtime, and this page does not cover state or local daily-overtime rules. Overtime also depends on whether the employee is covered and non-exempt, which the calculator cannot know. The Friday night shift crosses midnight, and the calculator adds it as one 9-hour line before the break; it does not split hours by calendar day.
Which breaks to subtract
Federal rules separate short rest breaks from real meal periods. A short break, typically running from 5 to about 20 minutes, must be counted as hours worked (29 CFR 785.18), so do not put it in the break box. A bona fide meal period is not work time, but the employee must be completely relieved from duty, and 30 minutes or more is typically enough (29 CFR 785.19). If you must keep working or stay at your post while you eat, it is not a true meal break and it stays in the total.
| In – out | Break entered | Hours worked | Why |
|---|---|---|---|
| 9:00 AM – 5:30 PM | 30 min | 8 h | A real meal period (30 minutes or more, fully off duty) is not work time, so enter it as the break. |
| 9:00 AM – 5:00 PM | None | 8 h | Two 15-minute coffee breaks inside the shift are rest periods. They stay in the total, so leave the break box empty. |
| 9:00 AM – 1:30 PM | None | 4 h 30 min | No meal period is taken, so there is nothing to subtract. |
The calculator only subtracts what you type in the break box. It does not decide whether a break is a rest period or a bona fide meal period, and it does not check any employer policy or state law.
Minutes to decimal hours
Timesheets and invoices often ask for hours as a decimal. The values below are minutes ÷ 60 rounded to two places. Adding rounded values piles up error, so when combining several entries add the minutes first and convert once at the end.
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 5 min | 0.08 | 25 min | 0.42 |
| 6 min | 0.10 | 30 min | 0.50 |
| 10 min | 0.17 | 40 min | 0.67 |
| 12 min | 0.20 | 45 min | 0.75 |
| 15 min | 0.25 | 50 min | 0.83 |
| 20 min | 0.33 | 55 min | 0.92 |
Six minutes is exactly 0.1 hour, so a log kept in 6-minute steps comes out to one decimal place with no rounding. That matters for payroll: the federal rule on time clocks accepts the long-standing practice of rounding to the nearest 5 minutes, one-tenth of an hour or quarter hour, as long as it averages out so employees are fully paid for all the time they actually work (29 CFR 785.48(b)). To go the other way, multiply the decimal part by 60: 7.75 hours is 0.75 × 60 = 45 minutes, so 7 h 45 min.
Adding work hours in Excel or Google Sheets
If your log is already in a sheet, put the start in column A, the end in column B and the break in minutes in column C, then work out each line in column D. Spreadsheets treat one day as 1, so the break minutes are divided by 1,440 before they are subtracted.
| Cell | Formula | Meaning |
|---|---|---|
| D2 | =MOD(B2-A2,1)-C2/1440 | End − start; MOD adds a day when the shift crosses midnight; then the break comes off |
| D total | =SUM(D2:D7) | Set the cell format to [h]:mm so totals over 24 hours show as 39:00 |
| Decimal hours | =SUM(D2:D7)*24 | With a number format this shows 39 |
If the total cell uses the ordinary h:mm format, 39 hours drops a whole day and shows as 15:00. When a time total in Excel looks too small, this format is usually why. For a line where you only know the length (Saturday, 1 h 30 min), just type 1:30 in the D cell.
Common calculation mistakes
- Writing 1 h 30 min as 1.30 hours: in decimal hours, 0.30 is 18 minutes. One hour thirty minutes is 1.50 hours.
- Getting a negative number across midnight: 10:00 PM – 7:00 AM worked as 7 − 22 gives −15 hours. Add a day and it is 9 hours.
- Subtracting a break twice: if you already split lunch into two lines, leave the break box empty. The gap between the two lines was never added.
- Adding up rounded decimals: three 20-minute entries are exactly 60 minutes, not 0.33 × 3 = 0.99 hours.
- Expecting overlaps to be counted once: this calculator adds each line separately. If you logged the same period in two apps, use the Overlapping Time Calculator, which counts overlapped time once.
Limits and cautions
- Times are to the minute and you can enter up to 50 lines. A length line takes up to 999 hours.
- Because dates are not entered, lines that overlap are each added in full. One line cannot be longer than 24 hours, so split longer records by date.
- A day is always 24 hours. For days when daylight saving time changes, or records in different time zones, convert everything to one time zone first.
- The result is only the sum of the times you entered. It is not a ruling on what counts as hours worked, on overtime, or a pay calculation.
- Everything is calculated inside this browser and nothing is sent or stored. The log goes into the address only when you press “Copy link”.
Sources
- 0129 CFR 785.18, RestShort rest breaks, running from 5 minutes to about 20 minutes, must be counted as hours worked
- 0229 CFR 785.19, MealBona fide meal periods are not worktime; the employee must be completely relieved from duty, and 30 minutes or more is typically enough
- 0329 CFR 785.48(b), RoundingRounding to the nearest 5 minutes, one-tenth or quarter of an hour is accepted if employees are fully compensated for all time worked
- 0429 U.S.C. 207(a)(1) and DOL Fact Sheet #23Overtime at one and one-half times the regular rate for hours over 40 in a workweek
- 05Microsoft Support: Format numbers as dates or timesElapsed-time format code [h]:mm (totals over 24 hours)
- 06NIST SP 811, Chapter 5: Units outside the SITable 6: 1 h = 60 min = 3,600 s, 1 d = 24 h
- 07WHATWG HTML Standard: time input (type=time)The value is a 24-hour “hh:mm” string; the displayed format may follow device settings
- 08Google Sheets API: Date and time format tokens[h+] = elapsed hours in a duration, so Google Sheets can also show totals over 24 hours
Frequently asked questions
How do I add several time intervals together?
Convert each time to minutes since midnight, subtract the start from the end on every line, take off any break, then add the lines. 9:00 AM – 12:00 PM and 1:00 PM – 6:00 PM are 180 and 300 minutes, 480 minutes in all, which is 8 hours.
Can I add plain lengths such as 1 h 45 min and 2 h 20 min?
Yes. Add a length line and enter the hours and minutes separately. 105 and 140 minutes make 245 minutes, which is 4 h 5 min. Start–end lines and length lines can be mixed and are added together.
How do I enter a shift from 10:00 PM to 7:00 AM the next day?
Enter 10:00 PM as the start and 7:00 AM as the end. Because the end is earlier than the start, the calculator treats it as ending the next day, adds a day and gets 9 hours. With a 1-hour break that is 8 hours.
Should I subtract breaks when adding work hours?
Under US federal rules, short rest breaks of about 5 to 20 minutes count as hours worked (29 CFR 785.18), so leave them out of the break box. A bona fide meal period, usually 30 minutes or more with the employee fully off duty, is not work time (29 CFR 785.19), so enter it.
How many hours and minutes is 39.50 decimal hours?
Multiply the decimal part by 60 to get minutes. 0.50 × 60 = 30 minutes, so 39.50 is 39 h 30 min. Be careful the other way round: writing 1 h 30 min as 1.30 actually means 1 h 18 min.
Are overlapping lines counted only once?
No. Dates are not entered, so the calculator cannot tell whether two lines fall on the same day, and each line is added separately. If you logged the same period twice, use the Overlapping Time Calculator to count overlapped time once.
My Excel time total looks too small once it passes 24 hours.
With the h:mm format the total wraps every 24 hours, so 39 hours shows as 15:00. Change the cell format to [h]:mm to see 39:00, and multiply the total by 24 to get decimal hours.
Is my log saved, and how many lines can I enter?
The log is calculated in your browser and is not saved. You can enter up to 50 lines, and pressing Copy link gives an address that holds the current log and goal so you can share it.