Time Adder & Subtractor (HH:MM:SS)
Enter each duration as hours, minutes and seconds — click "Add row" for more entries and toggle the + / − chip on each row to add or subtract. The widget instantly totals everything in HH:MM:SS, decimal hours, total minutes and total seconds, carrying seconds into minutes and minutes into hours automatically. No 24-hour wrap, no manual carrying. Useful for stacking video clip lengths, workout intervals, race splits, playlist totals or any scenario where you need to sum or subtract several time durations.
Time entries
Add as many rows as you need. Toggle each row's + / − to add or subtract.
Minutes and seconds must be 0–59; carry any 60+ into the column to the left.
Total (HH:MM:SS)
00:00:00
Other formats
- Decimal hours
- 0
- Total minutes (decimal)
- 0
- Total seconds
- 0
Formula
total_seconds = Σᵢ signᵢ × (hᵢ × 3600 + mᵢ × 60 + sᵢ) HH = ⌊|total| / 3600⌋ MM = ⌊(|total| mod 3600) / 60⌋ SS = |total| mod 60
- · Each row accepts 0–59 in the minutes and seconds columns; carry any value of 60 or more into the column to its left (this matches ISO 8601 and every spreadsheet engine).
- · Hours are uncapped — a weekly timesheet (38:45) or a multi-stage race total (5:42:10) display cleanly without wrapping at 24h.
- · Negative totals are supported: the result reads "−HH:MM:SS" so you can see at a glance how far the subtractions exceeded the additions.
- · Results are rounded to the nearest whole second to avoid IEEE-754 drift (so 0.1 + 0.2 + 0.7 lands exactly on 00:00:01, not 00:00:00.999).
- · The URL is kept in sync via an "e" param (e.g. e=+1:30:0,+0:45:30,-0:15:0); share or bookmark the link to restore every row.
- · This is pure mixed-radix arithmetic on durations — no calendars, time zones or daylight saving involved.
Frequently asked
How is this different from summing times in Excel or Google Sheets?
The arithmetic is identical, but the UX is friendlier. Excel stores a day as 1.0, so totals beyond 24 hours wrap back to 0 unless you remember to format the result cell as [h]:mm:ss — a frequent source of "where did my hours go?" bugs. This tool has no 24h cap by default and shows negative totals directly (spreadsheets need ABS + conditional formatting to mimic that). You also don't need any formulas or cell formatting tricks — just type each duration and read the result.
Why do I get a negative total? Did I do something wrong?
No — a negative total is intentional and means the subtracted entries summed to more than the added ones. The tool displays "−HH:MM:SS" with a "negative" hint. For example, computing "actual 7:30 − target 8:00" gives −00:30:00, meaning you came up half an hour short. If you simply want the magnitude of the difference, leave both as positive entries and flip the smaller one to the − sign. For elapsed time between two clock times (e.g. 09:00 to 17:30), use the Time Card calculator under Date & Time instead.
Can I enter fractional seconds, e.g. 1:23:45.5?
Yes. The inputs accept decimal values, so 45.5 seconds is added to the running total exactly. To dodge floating-point drift, the final HH:MM:SS readout (and every derived format) is rounded to the nearest whole second — so 0.1 + 0.2 + 0.7 lands on 00:00:01, not 00:00:00.999. Good enough for rough totals when editing audio or video, but for frame-accurate work (DaVinci, Premiere, Reaper) you should keep summation inside the professional tool itself.
What happens if my total exceeds 24 hours, like a weekly timesheet?
It just keeps going. Five 7:45 shifts read as 38:45:00 — the tool does not silently fold the result back into "1 day 14h 45m". If you do want a days/hours/minutes breakdown, divide total seconds by 86400 for days, the remainder by 3600 for hours, and so on — but most users find a flat HH:MM:SS readout easier to scan at a glance for weekly totals.
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