Decimal Hours ↔ HH:MM:SS Converter
A bidirectional Decimal hours ↔ HH:MM:SS converter. Enter hours, minutes and seconds to see decimal hours, total minutes and total seconds instantly; or enter a decimal value (e.g. 7.75) and the tool splits it back to 7:45:00. Built for payroll, timesheets, invoices, lab notebooks — or anywhere you need to turn "7h 30m" into "7.5" without fumbling on a phone calculator.
HH:MM:SS
Decimal hours
Enter a valid time: minutes and seconds must be between 0 and 59; hours can be positive or negative.
HH:MM:SS
07:30:00
Decimal hours
7.5 h
Total minutes
450 min
Total seconds
27,000 s
Values round to the nearest whole second. Edit either side (HH:MM:SS or decimal) and the other updates instantly.
Formula
decimal hours = h + m / 60 + s / 3600 total seconds = h × 3600 + m × 60 + s
- · Common reference: 15 min = 0.25 h, 30 min = 0.5 h, 45 min = 0.75 h, 20 min ≈ 0.333 h.
- · Results round to the nearest whole second to dodge floating-point drift — 0.1 h becomes exactly 0:06:00, not 0:05:59.
- · Minutes and seconds inputs accept 0–59 only; out-of-range values trigger an inline error. Hours can be negative (e.g. −2:30:00) for time differences.
- · In payroll, this decimal format is called "industrial minutes" or "decimal hours" — ADP, QuickBooks and SAP all store time this way internally.
- · The URL carries h, m, s and d parameters so you can share or bookmark a conversion.
- · The tool assumes a flat 24-hour day; daylight-saving transitions add or subtract 1 hour separately.
Frequently asked
Why does payroll convert HH:MM into decimal hours?
Because hourly rate × decimal hours yields wages directly (rate × 7.5 = half-day pay), whereas "rate × 7:30" is meaningless in a spreadsheet — only after conversion can SUM, PRODUCT and other arithmetic work. Virtually every payroll system and Excel timesheet stores time as decimal hours under the hood and formats it back to HH:MM for display.
Is 20 minutes 0.20 or 0.33 hours?
0.333… hours. 20 minutes = 20 ÷ 60 = 0.333… h, while 0.20 h is actually 12 minutes (0.20 × 60 = 12). This is the single most common mistake people make with decimal hours, because we read "20 minutes" on a clock face and instinctively think "0.20." But hours divide by 60, not 100. The converter sidesteps the error: change either side and it computes the correct match.
Can I enter values longer than 24 hours, like a 38:45 weekly total?
Yes. The tool has no upper bound on hours — the hours field accepts any integer (including negatives), so 38 hours 45 minutes converts to 38.75 hours, 2,325 minutes, 139,500 seconds. Handy for weekly totals, monthly project hours, or any cumulative timesheet. Note: minutes and seconds still cap at 0–59; carry into the hours column manually if you have ≥ 60 of either.
How do I turn decimal hours back into Excel’s [h]:mm format?
Excel stores one day as 1.0, so divide by 24: cell = decimal_hours / 24, then format the cell as [h]:mm or [h]:mm:ss (the square brackets allow values ≥ 24 hours to display without wrapping back to 0). 7.5 / 24 ≈ 0.3125 displays as 7:30. Google Sheets follows the same convention.
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