The formula
How to calculate working hours
Working hours are the hours you are paid for, which is the time between start and finish minus any unpaid break. The distinction matters for hourly rates, overtime thresholds and Working Time Regulations compliance.
Workers in the UK are entitled to an uninterrupted 20-minute rest break when working more than six hours a day. Whether it is paid is a matter for the contract — most employers make it unpaid.
Fill in the following:
- Hours between start and finish (hours)
- Unpaid break (minutes)
- Days per week (days)
No submit button: type and the answer moves. Your inputs end up in the link, so the page can be shared already filled in.
The order the fields are filled in makes no difference to the result — the calculator recomputes the whole formula from whatever is currently in every field, not step by step. That means it is safe to adjust one number, watch the result change, and adjust it back, without worrying about resetting anything first.
Why working hours matters
A calculation like this usually gets used at a decision point rather than out of curiosity — comparing two real options, checking a number a lender or adviser has quoted, or working out whether a plan that sounded fine in conversation still holds up once it is written down with actual figures. The maths itself is rarely complicated; what is hard is remembering which figures to use and in what order, which is exactly what a dedicated calculator is for.
It is also useful as a sense check before signing anything. A quote, an offer letter or a spreadsheet from someone else can contain an error, an optimistic assumption, or simply a different convention for rounding — running the same inputs through an independent calculator is a quick way to confirm a number before relying on it.
The reason a page like this exists at all, rather than leaving the calculation to a spreadsheet or a textbook appendix, is that the formula behind working hours is fiddly enough to get wrong by hand but not complicated enough to need specialist software. That middle ground — real enough maths to matter, simple enough to check instantly — is exactly what a dedicated calculator is for, and it is why the same figure recalculated here should match a careful manual calculation almost exactly.
A calculator like this one is often bookmarked and returned to repeatedly over months rather than used once, particularly for anything tied to an ongoing plan such as a mortgage, a savings goal or an investment being tracked. Because the figures live in the web address rather than only in memory, coming back to the same page with updated numbers is quicker than starting from a blank spreadsheet each time.
Worked example
Here is the calculation with the starting values:
- Hours between start and finish: 8.5 hours
- Unpaid break: 45 minutes
- Days per week: 5 days
That gives:
- Paid hours per day: 7.75 hours
- Paid hours per week: 38.75 hours
- Paid hours per year: 2,015 hours
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
A 45-minute unpaid break across a five-day week is nearly four hours, or roughly 195 hours a year. Over a career that is a substantial amount of time that is neither worked nor paid.
Where this goes wrong. Travel between appointments counts as working time for mobile workers, as does time spent on call at the workplace. Both are commonly and incorrectly excluded.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
An average of 48 hours a week over a 17-week reference period, under the Working Time Regulations. You can opt out in writing, and you can withdraw that opt-out with notice.
No. The statutory 20-minute break must be given but need not be paid unless the contract says so. It also has to be a genuine break away from the workstation.
The answer it gives you is paid hours per day. With 8.5 hours hours between start and finish, 45 minutes unpaid break and 5 days days per week, that comes to 7.75 hours. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.