Pro Rata Sick Leave Calculator — Free Tool for UK, US & More
Whether you’re a part-time worker, a new starter mid-year, or an HR manager trying to calculate sick leave entitlement fairly, working out pro rata sick leave can feel confusing. This free pro rata sick leave calculator does the hard work for you — instantly and accurately.
Use the tabs above for three scenarios: standard full-time sick leave, part-time or reduced-hours calculations, and mid-year new starter entitlements.
What Is Pro Rata Sick Leave?
“Pro rata” is a Latin phrase meaning “in proportion.” When applied to sick leave, it means an employee’s sick leave entitlement is calculated in proportion to the hours or days they work, compared to a full-time equivalent (FTE).
If a full-time employee is entitled to 10 days of sick leave per year, a part-time employee working half the hours would be entitled to 5 days. Simple in principle — but the calculations can get complicated quickly when salaries, start dates, and pay rates are involved.
Pro rata sick leave applies in two main situations:
- Part-time or reduced-hours workers — entitlement is scaled to their FTE ratio
- New starters mid-year — entitlement is scaled to the remaining fraction of the leave year
How to Calculate Pro Rata Sick Leave
The Basic Formula
For part-time employees, the formula is:
Pro Rata Sick Days = (Employee’s Hours Per Week ÷ Full-Time Hours Per Week) × Full-Time Sick Entitlement
Worked Example (UK)
Sarah works 25 hours per week. Her employer’s full-time hours are 37.5 per week and the full-time sick leave entitlement is 10 days per year.
- FTE ratio: 25 ÷ 37.5 = 66.7%
- Pro rata sick days: 10 × 66.7% = 6.67 days
If Sarah’s annual salary is £18,750 (pro rata from £28,125 full-time) and she receives full pay during sick leave:
- Daily rate: £18,750 ÷ 260 = £72.12/day
- Total sick pay value: £72.12 × 6.67 = £480.80
Worked Example (US)
James is a part-time employee in California working 20 hours per week. Full-time is 40 hours. His employer offers 10 days sick leave per year.
- FTE ratio: 20 ÷ 40 = 50%
- Pro rata sick days: 10 × 50% = 5 days
- If his annual salary is $30,000, his daily rate is $30,000 ÷ 260 = $115.38/day
- Sick pay value: $115.38 × 5 = $576.90
How to Calculate Pro Rata Sick Leave for New Starters
If an employee joins part-way through the leave year, their sick leave entitlement is usually calculated on a pro rata basis for the remainder of that year.
Formula:
Pro Rata Sick Days = (Calendar Days Remaining in Year ÷ 365) × Full-Time Sick Entitlement
Worked Example
Emma joins on 1 September. Her employer’s leave year runs to 31 December (122 remaining calendar days).
- Year fraction: 122 ÷ 365 = 33.4%
- Full-time entitlement: 10 days
- Emma’s pro rata sick days: 10 × 33.4% = 3.34 days
Many employers round to the nearest half-day. Some have a qualifying period (typically 3 or 6 months) before any contractual sick pay is payable — though UK Statutory Sick Pay (SSP) applies from day one of employment.
UK Sick Leave Rules: What You Need to Know
In the UK, sick leave entitlement has two layers: statutory (the legal minimum) and contractual (what your employer offers on top).
Statutory Sick Pay (SSP)
- SSP is £116.75 per week (2025/26 rate)
- It is payable from the 4th day of absence (first 3 “waiting days” are unpaid)
- It can be paid for up to 28 weeks
- You must earn at least the Lower Earnings Limit (£123/week in 2025/26) to qualify
- Full guidance is available at GOV.UK statutory sick pay
Contractual Sick Pay
Many employers offer enhanced sick pay above SSP — for example, full pay for the first 4 weeks, then half pay for the next 4 weeks, then SSP. The exact terms depend on your employment contract.
For more on your rights, ACAS guidance on sick pay entitlement is the clearest public-sector resource in the UK.
Part-Time Workers’ Rights
Under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, part-time workers cannot be treated less favourably than comparable full-time workers. This means pro rata sick leave entitlement must mirror the full-time equivalent — you cannot simply give part-timers the same number of days as full-timers without scaling the pay proportionally.
Pro Rata Sick Leave in the US, Australia & Canada
United States
Unlike the UK, the US has no federal statutory sick leave law. Sick leave rules vary by state and employer. However, several states have mandatory paid sick leave, including California, New York, Washington, and Massachusetts.
For federal employees, the Office of Personnel Management sets rules: full-time workers accrue 13 days of sick leave per year; part-time workers accrue sick leave on a pro rata basis.
US Example
A part-time federal employee working 20 hours per week (50% of full-time 40 hours) accrues:
- Full-time accrual: 13 days/year
- Pro rata: 13 × 50% = 6.5 days/year
Australia
Under the National Employment Standards (NES), full-time employees are entitled to 10 days of paid personal/carer’s leave per year. Part-time employees receive this entitlement on a pro rata basis. The Fair Work Ombudsman provides full guidance.
Australian Example
A part-time employee working 3 days (24 hours) per week in a 5-day (38-hour) full-time role:
- FTE ratio: 24 ÷ 38 = 63.2%
- Pro rata sick leave: 10 × 63.2% = 6.32 days
Canada
In Canada, the Canada Labour Code provides federally regulated employees with 10 days of paid medical leave per year after 30 days of continuous employment. Provincial rules vary. Part-time workers generally receive pro rata entitlement.
Pro Rata Sick Pay Calculation: Full Pay vs Half Pay vs SSP
Understanding the difference between types of sick pay is critical for accurate calculations.
Full Pay
The employee receives their normal salary during sickness absence. The sick pay value equals:
Daily Rate × Number of Sick Days Taken
Half Pay
Common in public sector roles and some large employers. The sick pay value equals:
(Daily Rate × 50%) × Number of Sick Days
SSP Only
Where an employer offers no contractual sick pay, SSP applies. Note that SSP is a fixed weekly amount (£116.75 in 2025/26) — it is not a percentage of salary, so high earners receive the same SSP as low earners.
Our calculator above handles all three scenarios for both full-time and part-time workers.
Common Questions About Pro Rata Sick Leave
How many sick days are employees entitled to in the UK?
There is no statutory entitlement to a specific number of sick days in the UK. The legal minimum is SSP (up to 28 weeks), but how many days of full or enhanced pay you receive depends entirely on your employment contract. Most employers offer between 5 and 30 days of full pay per year.
Can an employer reduce sick leave entitlement for part-time workers?
No — not proportionally below the full-time equivalent. Under Part-time Workers Regulations, a part-timer working 50% of full-time hours must receive at least 50% of the full-time sick leave entitlement.
Does pro rata sick leave apply to zero-hours contract workers?
Zero-hours workers may be entitled to SSP if they meet the earnings threshold. Contractual sick pay eligibility depends on whether they have a contract of employment and the specific terms. This area is legally complex — seek advice from ACAS if unsure.
Is pro rata sick leave rounded up or down?
There is no legal requirement either way. Most employers round to the nearest half-day or whole day in the employee’s favour. Check your employment contract or HR policy for your employer’s specific rounding rule.
Related Calculators You May Find Useful
If you’re calculating sick leave, you may also need to work out related figures for the same employee. Our other tools cover:
- Pro Rata Holiday Calculator — calculate part-time holiday entitlement in hours
- Pro Rata Salary Calculator — work out the salary for part-time or part-year work
- Pro Rata Take Home Pay Calculator — calculate net pay after tax and NI
- Pro Rata Days Calculator — calculate entitlements for partial periods
- Pro Rata Holiday Calculator for Leavers — calculate unused holiday when someone leaves part-way through a year
- Pro Rata Term-Time Salary Calculator — for school and term-time workers
Frequently Asked Questions
Q: How do you calculate pro rata sick leave for a part-time worker?
Divide the employee’s weekly hours by the full-time weekly hours to get the FTE ratio. Multiply the full-time sick leave entitlement by this ratio. For example, 20 hours ÷ 40 hours × 10 days = 5 days entitlement.
Q: How much sick leave do I accrue each month?
If your annual entitlement is 10 days, you accrue approximately 0.83 days per month (10 ÷ 12). Some employers use an accrual model; others grant the full entitlement at the start of the year.
Q: How to calculate pro rata sick leave for a new starter?
Divide the number of calendar days remaining in the leave year by 365, then multiply by the full-year entitlement. If 90 days remain and the full entitlement is 10 days: 90 ÷ 365 × 10 = 2.47 days.
Q: What is the difference between pro rata sick leave and SSP?
SSP (Statutory Sick Pay) is a fixed weekly legal minimum (£116.75/week in the UK) paid by employers. Pro rata sick leave refers to the number of days of absence an employee is entitled to — which, for part-timers, is a proportion of the full-time entitlement. The two are separate concepts: you can have pro rata sick leave entitlement that is paid at SSP rate, full pay, or half pay.
Q: Does a part-time worker get the same number of sick days as a full-time worker?
No — under UK law, sick leave for part-time workers is pro rated. A part-timer working 3 days per week (60% of a 5-day week) would receive 60% of the full-time entitlement. Giving them the same number of days as a full-timer would actually be more generous than required — the law requires equal treatment proportionally, not identically.
Q: Can I take more sick days than my pro rata entitlement?
You can be absent for longer, but once your paid sick leave entitlement is exhausted, your pay may drop to SSP or to nothing (depending on your contract). Extended absence beyond 28 weeks takes you out of SSP eligibility entirely.
Q: Is pro rata sick leave calculated the same in Australia as in the UK?
The formula is the same (FTE ratio × full-time entitlement), but the entitlement differs. Australia’s NES provides 10 days personal/carer’s leave per year for full-timers; the UK has no statutory paid sick day entitlement (only SSP after qualifying days). Always check the rules for your specific country and employment type.
Q: What happens to unused pro rata sick leave?
Unlike holiday leave, unused sick leave generally does not carry over or get paid out when you leave a job. Sick leave is for use when ill, not a saved benefit. Some employers operate “well-being days” differently — check your contract.
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