TimerPlanDecimal hours on a timesheet
Seven hours and thirty minutes is 7.5 decimal hours, because thirty minutes is half of sixty — not 7.30, which claims seven hours and eighteen minutes. The rule is minutes divided by sixty, and it is the whole of the conversion.
Entered wrongly on a daily timesheet, the error is twelve minutes a day. Over a working year that is roughly forty-eight hours, which for most people is more than a week of pay.
It survives because 7.30 is a plausible-looking number in a field that expects a decimal, so nothing in the system flags it and nobody notices until an audit compares hours to rotas.
The table worth keeping
| Minutes | Decimal | Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|---|---|
| 5 | 0.08 | 25 | 0.42 | 45 | 0.75 |
| 6 | 0.10 | 30 | 0.50 | 48 | 0.80 |
| 10 | 0.17 | 35 | 0.58 | 50 | 0.83 |
| 12 | 0.20 | 36 | 0.60 | 55 | 0.92 |
| 15 | 0.25 | 40 | 0.67 | 60 | 1.00 |
| 20 | 0.33 | 42 | 0.70 |
Two rows are worth noticing. Six minutes is exactly 0.1 hours, which is why US payroll so often rounds to six-minute blocks — the decimal stays clean. And 20 minutes is 0.33, not 0.20, which is the single most common wrong entry after the half hour.
Where it actually goes wrong
On the form. Somebody works 7:45 and types 7.45. The claim is seven hours and twenty-seven minutes; the loss is eighteen minutes for that day.
In a spreadsheet. A column of times entered as 7.30, 8.15, 7.45 adds up perfectly and means nothing, because the cells were never times. Spreadsheets will do this silently unless the cells are formatted as duration, and the total will look plausible.
In an invoice. Billing 2.30 for two and a half hours is a five per cent discount nobody asked for. Over a year of consultancy it is the difference between a good month and an average one.
How to stop making it
Keep the log in the unit the form wants. If payroll takes decimals, record decimals from the start — the hours calculator and the time card calculator both print h:mm and decimal side by side for exactly this, and the weekly timesheet log keeps the week in decimal as you go.
When the times come from a running clock rather than from memory, the stopwatch and the count-up timer are where they start, and the time duration calculator turns a pair of clock times into every form at once.
Frequently asked questions
What is 45 minutes in decimal hours?
0.75, because forty-five is three quarters of sixty. The six values worth memorising are 15 minutes at 0.25, 20 at 0.33, 30 at 0.5, 40 at 0.67, 45 at 0.75 and 50 at 0.83. Everything else is minutes divided by sixty, and the hours calculator prints both forms so the conversion never has to happen in your head.
Why does payroll use decimal hours at all?
Because pay is hours multiplied by a rate, and multiplying 7:30 by an hourly rate is meaningless until it becomes 7.5. Once a system works in decimals it wants its inputs in decimals, and the clock form is the one that has to be converted. It is a machine’s convenience that has been pushed onto the person filling in the form.
Is rounding to a quarter hour allowed?
In the US, yes, as long as it does not consistently favour the employer — the rule permits rounding to the nearest quarter hour, and rounding that is always downwards is not rounding but unpaid work. Six-minute rounding is the other common option, and it exists because six minutes is exactly a tenth of an hour, so the decimal figure comes out clean.
Which way should I round when the tenth does not divide evenly?
To the nearest, and let it average out — that is the assumption the rule is built on. Systematic rounding in one direction is what turns an accounting convenience into an underpayment, and it is visible as soon as anyone compares a month of rounded totals against the raw ones.
How do I check a payslip against my own record?
Convert your own hours to decimal first, then compare. Comparing 37:30 against 37.5 is the same number; comparing 37:30 against 37.30 is not, and the difference is where most payroll disputes start. Keeping a log in decimal hours from the beginning removes the conversion entirely.
How this works
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