Working backwards from a target salary
Most pro rata questions run one way: “I work these hours — what will I earn?” This calculator runs the other way, for the equally common question: “I need to earn this much — how many hours is that?” It is the sum people do when they are reducing their hours after parental leave, weighing up a four-day week, or checking whether a part-time version of a job still covers their outgoings.
The logic is the ordinary pro rata formula turned inside out. Your pay is the full-time salary multiplied by your fraction of the week, so your fraction must be the target divided by the full-time salary. Multiply that fraction by the full-time hours and you have the hours. The same fraction is your FTE, and dividing the hours by the length of a full-time day gives the answer in days.
Two honest limits. First, this works in gross pay — tax, National Insurance and pension contributions come off afterwards, so the hours needed for a take-home target will be a little higher. Second, if the hours come out above the full-time week, the target is not reachable on pro rata terms at that job: something else has to close the gap. When you have your hours, run them through the salary calculator to see the full breakdown.
Frequently asked questions
It depends on the full-time salary and hours for the job. Work out the full-time hourly rate (full-time salary ÷ full-time hours ÷ 52), then divide your target pay by that rate and by 52. On a £40,000 job at 40 hours a week (£19.23 an hour), earning £30,000 takes 30 hours a week — a 0.75 FTE.
No. It works in gross pay, before income tax, National Insurance and pension deductions, in the same way as the salary figures in job adverts. Your take-home pay will be lower and depends on your tax code and pension contributions.
Then the target cannot be reached on pro rata hours alone at that job's hourly rate. You would need overtime, a higher-paid role, or a pay rise. The calculator notes this when your target is above the full-time salary.
Divide the hours by the length of one full-time day (full-time hours ÷ 5). At 40 hours a week a full-time day is 8 hours, so 24 hours a week is 3 full days. The calculator shows the days figure alongside the hours.