Hours Calculator Guide

Calculating hours is essential for tracking work time, managing projects, billing clients, or planning your day. This guide covers all aspects of time calculation—from simple duration finding to complex multi-day timesheet totals.

Calculating Hours Between Two Times

The most common time calculation is finding how many hours between a start and end time:

When Times Include Minutes

For precise calculations with minutes, convert to total minutes first:

Adding Hours and Minutes

To add multiple time periods together:

Decimal Hours Conversion

Many payroll systems use decimal hours. Here's how to convert:

Minutes to Decimal

Decimal to Minutes

Overnight Time Calculation

When calculating hours that span midnight:

Subtracting Breaks

To calculate actual working hours:

Common Work Hour Calculations

Billing in Time Increments

Many professionals bill in set increments:

Time Zone Calculations

When working across time zones, add or subtract the difference:

Annual Hours Calculation

For full-time equivalent (FTE) planning:

Quick Reference: Time Conversions

Understanding Time Calculations in UK Workplaces

Accurate hours calculation is fundamental to UK employment law and payroll. The Working Time Regulations 1998 limit the average working week to 48 hours, calculated over a 17-week reference period. Workers can opt out of this limit voluntarily, but employers must keep records of hours worked for all employees. Understanding how to calculate hours correctly ensures compliance with these regulations and accurate pay calculations, particularly for workers paid by the hour or those claiming overtime.

Converting between decimal hours and hours-and-minutes is essential for payroll processing. Most UK payroll software works in decimal hours, where 7 hours and 30 minutes is entered as 7.50, and 7 hours and 45 minutes is entered as 7.75. Converting minutes to decimal requires dividing by 60: 15 minutes equals 0.25 hours, 30 minutes equals 0.50, and 45 minutes equals 0.75. Common mistakes include treating 7:30 as 7.30 decimal hours (which actually represents 7 hours and 18 minutes) rather than the correct 7.50 decimal hours.

For workers on zero-hours contracts, which are used by approximately 3 percent of UK employees, tracking cumulative hours is important for several reasons. Hours worked determine eligibility for various employment rights, including holiday entitlement (which accrues from the first hour worked), statutory sick pay (which requires average weekly earnings above the lower earnings limit), and auto-enrolment in a workplace pension (which triggers at specific earnings thresholds). Maintaining accurate records of hours worked protects workers' rights and ensures they receive all statutory entitlements.

Practical Applications of Hours Calculations

Hours calculations extend well beyond the workplace. Project planning, study timetabling, and personal productivity all benefit from accurate time mathematics. Students preparing for exams often use hours calculations to allocate revision time across subjects. A student with 10 GCSE subjects and 4 weeks before exams might calculate: 4 weeks x 7 days x 5 study hours = 140 total hours, divided by 10 subjects = 14 hours per subject, which can then be distributed based on each subject's difficulty and exam weighting.

Freelancers and self-employed workers in the UK need hours calculations for pricing and invoicing. The national minimum wage (£12.21 per hour for workers aged 21 and over in 2025/26) provides a useful benchmark, but most freelancers charge significantly more to account for unbillable time, administrative overhead, pension contributions, and holiday pay that they must fund themselves. A freelancer targeting £40,000 annual income who can bill 1,200 hours per year (approximately 25 billable hours per week after holidays and admin) needs to charge at least £33.33 per hour, which is the kind of calculation that effective hours tracking makes possible.

Time zone calculations are another practical application in an increasingly globalised world. UK businesses working with international clients must calculate meeting times across time zones, accounting for GMT versus BST (British Summer Time). The clocks change on the last Sunday of March (spring forward) and the last Sunday of October (fall back), shifting the UK's offset from UTC+0 to UTC+1 during summer months. This affects scheduled calls and deadlines with partners in different time zones and can cause confusion if not carefully tracked.

Frequently Asked Questions

How do I calculate hours worked with a lunch break?

Subtract the lunch break duration from the total time between your start and end times. If you start at 9:00 AM and finish at 5:30 PM with a 1-hour unpaid lunch break, the calculation is: total elapsed time is 8 hours 30 minutes, minus 1 hour for lunch, equals 7 hours 30 minutes (7.50 decimal hours). If you take a shorter 30-minute break, the result is 8 hours (8.00 decimal hours). Always check your employment contract to determine whether breaks are paid or unpaid, as this affects the total hours recorded for payroll.

What is the difference between clock hours and decimal hours?

Clock hours use the standard 60-minute hour format (e.g., 7 hours 45 minutes), while decimal hours convert the minutes into a fraction of an hour (e.g., 7.75 hours). Decimal hours are used in payroll and accounting because they are easier to multiply for pay calculations. To convert: divide the minutes by 60 and add to the hours. So 7 hours 20 minutes becomes 7 + (20/60) = 7.33 decimal hours. To convert back: take the decimal portion and multiply by 60. So 7.33 becomes 7 hours and 0.33 x 60 = 20 minutes.

How many working hours are there in a UK year?

A standard UK working year with a 37.5-hour week contains 1,950 hours before deducting annual leave. With the minimum statutory holiday entitlement of 28 days (5.6 weeks including bank holidays), the working hours reduce to approximately 1,740 hours. Workers with more generous holiday allowances of 30 to 35 days would work approximately 1,650 to 1,700 hours per year. These figures are important for salary-to-hourly-rate conversions, as dividing an annual salary by actual working hours gives the true effective hourly rate, which may be significantly higher than the nominal hourly rate calculated from a simple 52-week year.

Emma Thompson

Senior Content Editor

Emma is a senior content editor with a background in financial journalism. She specialises in making UK regulations and calculator tools understandable for consumers, working closely with qualified professionals to ensure accuracy.