Understanding Hourly to Annual Conversion

When you need to calculate pro rata salary for a part-time role or compare job offers, the basic formula is straightforward: multiply your hourly rate by your contracted weekly hours, then by 52 weeks. For a standard 37.5-hour week, that means annual ≈ hourly × 37.5 × 52. But this simple calculation hides several nuances that trip up many job seekers.

According to the Office for National Statistics (ONS) Annual Survey of Hours and Earnings (ASHE) for 2025, the median gross annual earnings for full-time employees were £39,039, equivalent to roughly £20.02 per hour at 37.5 hours per week. The median hourly rate (excluding overtime) was £19.67. These figures are a useful benchmark, but remember they are provisional and based on a 1% sample of PAYE records.

The National Living Wage and Minimum Wage

The government sets minimum hourly rates that apply to most workers. For the 2026/27 tax year, the National Living Wage (NLW) for workers aged 21 and over is £12.71 per hour. At 37.5 hours per week, that gives an annual salary of about £24,784.50. The previous year (2025) the NLW was £12.21, so rates increase annually. Always check the latest rates on GOV.UK.

Common Myths About Overtime Pay

One of the biggest misconceptions is that overtime must be paid at time-and-a-half. In reality, there is no statutory requirement for a premium rate. Many salaried employees receive plain time (their normal hourly rate) for extra hours, and some contracts include unpaid overtime for certain roles. The only legal requirement is that your average hourly pay across all hours worked does not fall below the National Minimum Wage.

Another myth is that overtime is always voluntary. Some contracts require you to work reasonable overtime as part of your duties. If you are unsure, check your employment contract or speak to your HR department. When you calculate pro rata salary for a role that includes guaranteed overtime, include those hours in your weekly total to get an accurate annual figure.

Overtime and Pro Rata Calculations

If you work part-time but regularly do overtime, your pro rata salary should reflect the total hours you are contracted to work, not just the basic part-time hours. For example, a 20-hour-per-week contract with a guaranteed 5 hours of overtime each week means your effective weekly hours are 25. Use that figure when converting to annual salary.

Pro Rata Salary: What It Really Means

Pro rata simply means 'in proportion'. Employers use it to calculate pay for part-time workers based on the full-time equivalent (FTE) salary. The FTE is usually based on a standard working week – often 37.5 hours for NHS roles, 35 hours for some office jobs, or 40 hours in retail.

To calculate pro rata salary, you need:

• The full-time annual salary for the role
• Your contracted weekly hours
• The full-time weekly hours (FTE)

Formula: (Your hours / FTE hours) × Full-time annual salary = Your pro rata salary

But beware: this gives you the basic salary. You also need to factor in:

• Holiday pay: Part-time workers are entitled to the same pro rata holiday as full-time colleagues. Some employers include holiday pay in the hourly rate (rolled-up holiday pay), which can affect the effective hourly rate.
• Pension contributions: These are often based on your actual earnings, so your take-home may differ.
• London weighting or location allowances: If applicable, add these to the annual figure before dividing.

NHS Pay Scales Example

The NHS uses clear pay bands with annual and hourly rates. For 2026/27, Band 5 (newly qualified nurses, for instance) starts at £16.40 per hour, while Band 6 starts at £20.44 per hour. These rates include Higher Cost Area Supplements (HCAS) for London and surrounding areas. If you work part-time in the NHS, your pro rata salary is calculated using the full-time band rate and your contracted hours. The NHS Employers website provides detailed pay scales.

Using the Hourly to Salary Tools

Our Hourly to Salary converter lets you quickly see annual equivalents based on your hours per week. For more detailed comparisons, visit our salary data page which includes median earnings by occupation and region. Remember that these tools assume a steady contracted week with no unpaid overtime, bonuses, or salary sacrifice. Actual pay depends on your rota, holiday pay method, and any London weighting.

Why Accurate Conversion Matters

Misunderstanding pro rata can lead to accepting a job that pays less than expected. For example, a role advertised as £30,000 pro rata for 20 hours per week might actually be £15,000 if the FTE is 40 hours. Always confirm the FTE hours and whether the salary includes any supplements.

Final Thoughts

When you calculate pro rata salary, always start with the full-time equivalent and adjust for your hours. Don't assume overtime is paid at a premium, and check whether location allowances are included. Use official sources like ONS and GOV.UK for benchmarks, and consult your contract for the exact terms. By avoiding these common myths, you can make informed decisions about job offers and negotiate with confidence.