Weekly Hours Calculator

What counts as annual working hours

Annual working hours are a contractual week carried across a full year: weekly hours × 52. A 40-hour week is 2,080 hours a year, a 35-hour week is 1,820. It is a contractual figure rather than a record of time spent at a desk, which is exactly why it is the one used to cost a role, to turn a salary into an hourly rate and to compare two offers that quote different weeks.

Hours actually worked is a second and smaller number: the annual figure less paid leave and public holidays. Five weeks of leave and ten public holidays take a 40-hour contract from 2,080 down to roughly 1,800. Measured averages for whole economies land lower again, around 1,700 across the OECD, because they count part-time workers alongside full-time ones.

The monthly figure is where this goes wrong most often. A month is 52 ÷ 12 weeks, about 4.33 and not four, so a 40-hour week is 173.33 hours a month rather than 160. Payroll divides by 173.33 for that reason, and a 160 inside a calculation is usually the fingerprint of a week multiplied by four.

The four-week month is the error

Multiplying a week by four to get a month is the single most common mistake in this arithmetic, and it is always wrong in the same direction. Four weeks a month is 48 weeks a year; the year has 52. The shortfall is a full month of work, about 8%, which is enough to make a staffing plan short, a budget wrong, or a contractor’s quote unprofitable.

The correct conversion is weekly × 52 ÷ 12, which is weekly × 4.333. For a 40-hour week that is 173.33 hours a month rather than 160. Payroll systems that work in monthly hours use 173.33 for exactly this reason, and a figure of 160 in a calculation is usually a sign that someone multiplied by four.

What each number is for

• Hours a month converting a monthly salary into an hourly rate, or the reverse. This is the divisor, and using 160 instead of 173.33 overstates the hourly rate by 8%.
• Hours a year comparing contracts, costing a role, or checking an annualised-hours agreement. 2,080 is the standard full-time year in the US; 1,820 is nearer the norm for a 35-hour European week.
• Working days a year capacity planning. Days a week × 52, minus leave and public holidays, is how many days a person is actually available: typically around 228 of a nominal 260.
• Full-time equivalent headcount planning and pro-rata pay. Two people at 0.5 FTE are one full-time post for budgeting, and the FTE share is what a part-time salary, holiday allowance and pension contribution are usually calculated from.

Why hours a year is the honest comparison

Salaries are quoted annually and work is done weekly, so comparing two jobs means putting them on the same footing. A €45,000 job at 35 hours a week and a €48,000 job at 42 are not three thousand euros apart: they are €24.70 an hour against €22.00, and the lower salary pays better per hour worked.

Leave belongs in that comparison too. Two contracts on the same salary and the same week are not equal if one has 20 days of leave and the other 30: the second buys two extra weeks of life at the same price. Working days a year is where that difference becomes visible, which is why it sits next to the hours here.

What a scaled week cannot tell you

This assumes every week is the same, which is true of a contract and not of a year. Shift patterns, seasonal peaks, annualised-hours schemes and term-time working all distribute the same annual total unevenly, and for those the annual figure is the only one of these numbers that stays true.

It also says nothing about whether the hours are lawful. Maximum weekly hours, minimum rest and the rules on night work are set by law and by collective agreement, and they differ by country and sector. The figures here are the input to that check, not the check itself.