Hours Calculator — Add, Subtract & Convert Time
Three tools in one: stack multiple time durations to get a running total, enter a start and end time to find the exact duration, or flip between H:MM and decimal hours for payroll and billing. All calculations run instantly in your browser — no signup needed.
- Total (H:MM:SS)
- 4:15:00
- Decimal hours
- 4.25
- Total minutes
- 255
How it works
Adding and subtracting time durations
Time arithmetic trips people up because minutes and seconds don't follow decimal rules — 90 minutes is 1 hour 30 minutes, not 1.90 hours. The Add/Subtract tab handles this automatically: enter each duration in hours, minutes, and seconds, choose whether each row adds to or subtracts from the running total, and read off the answer in both H:MM:SS and decimal form.
A common workplace scenario is reconciling a timesheet where you worked 3 h 45 min in the morning, took a 45-minute lunch, and put in 2 h 20 min in the afternoon. Stack those three rows (using − for the break if you want to exclude it) and the calculator adds them up instantly. It also flags negative totals — useful when checking whether scheduled hours exceed a budget.
The second row onwards lets you toggle between + and −. The first row is always addition because it anchors the total. You can add up to ten rows, covering a full split shift or a week of daily hours in a single calculation.
Converting hours to decimal for payroll and billing
Payroll software and invoicing systems almost always store time as a decimal number: 1.5 hours, not 1:30. The conversion is straightforward — divide the minutes by 60 and add the whole hours — but it's easy to make a rounding error when doing it by hand for a dozen line items.
The Hours to Decimal tab converts either way. Going from H:MM to decimal, enter the hours and minutes and the decimal equivalent appears immediately: 7:20 becomes 7.3333 hours, 0:45 becomes 0.75, 2:15 becomes 2.25. Going from decimal to H:MM, paste in the number your payroll system gave you and confirm it matches the clock time you expected.
Attorneys, consultants, and freelancers who bill in tenths or quarters of an hour (0.1 h = 6 min, 0.25 h = 15 min) can use this tab to cross-check their time entries before submitting invoices. A small rounding difference on every entry can add up to a significant discrepancy across a busy month.
Calculating time differences for scheduling and time tracking
The Time Difference tab answers questions like: How long is my commute if I leave at 8:15 AM and arrive at 9:02 AM? How many hours did I work if I clocked in at 7:45 and out at 16:30? You can type times in 12-hour format (9:00 AM, 1:30 PM) or 24-hour format (09:00, 13:30) — the calculator accepts both.
Night-shift workers face a special case: if you start at 10:00 PM and finish at 6:30 AM, the naive difference is negative. Tick the 'crosses midnight' checkbox and the calculator adds 24 hours to the end time, giving the correct 8:30 duration. The result shows hours:minutes:seconds, decimal hours, total minutes, and total seconds so you can plug the number directly into whatever system you are using.
For scheduling, total minutes and total seconds are handy when working with systems that store durations in a single unit — for example, a video editor showing clip lengths in seconds, or a database field measured in minutes. Read off the exact figure without doing a second conversion.
Frequently asked questions
›How do I add 2 hours 45 minutes and 1 hour 30 minutes?
Open the Add/Subtract tab. In the first row enter 2 hours and 45 minutes. Click 'Add row', then enter 1 hour and 30 minutes. The total shown is 4:15:00 (4 hours 15 minutes), or 4.25 decimal hours.
›What is 1:45 as a decimal?
1 hour 45 minutes equals 1.75 decimal hours. The formula is 1 + (45 / 60) = 1.75. Use the Hours to Decimal tab with 1 hour and 45 minutes to confirm.
›How do timesheets use decimal hours?
Most payroll and billing software stores time as a decimal rather than H:MM because decimal values can be multiplied directly by an hourly rate. For example, 7.5 hours times $20/h gives $150 without any conversion. Common conversions: :15 = 0.25, :20 = 0.333, :30 = 0.5, :45 = 0.75.
›How do I calculate hours between 9:00 AM and 5:30 PM?
Use the Time Difference tab. Enter 9:00 AM as the start time and 5:30 PM (or 17:30) as the end time. The result is 8:30:00, or 8.5 decimal hours.
›My shift crosses midnight — how does the calculator handle that?
On the Time Difference tab, tick the 'crosses midnight' checkbox. If you enter 10:00 PM start and 6:30 AM end, the calculator adds 24 hours to the end time and returns 8:30:00 as the duration.
›Can I subtract time to find a remaining balance?
Yes. On the Add/Subtract tab, use the − selector on any row after the first to subtract that duration from the running total. For example, start with 8:00:00 and subtract a 0:30:00 break to get 7:30:00 net working time.
›What does 2.333 decimal hours convert to in H:MM?
Switch the Hours to Decimal tab to 'Decimal to H:MM' mode and enter 2.333. The result is 2:20:00 (2 hours and 20 minutes), because 0.333 x 60 = 19.98 minutes, rounded to 20.
›Is this calculator useful for video production?
Yes. Video editors often need to add clip durations or confirm that a sequence fits a time slot. Enter each clip's H:MM:SS length as a row in the Add/Subtract tab and read the total. The total seconds figure is useful for systems that index clips by frame count.
Related tools
Last updated: