Guide

Part-Time Pro Rata Pay: Working Out a 3-Day-a-Week Salary (2026)

By Miguel Lin · Last updated June 30, 2026

Going part-time should be simple math: work three days instead of five, earn three-fifths of the salary. But the moment you see the actual figure on a contract, it’s surprisingly easy to wonder whether it’s been worked out fairly — especially when the advert quoted the full-time number and your offer quotes something smaller. The walkthrough below checks you’re getting your full proportion; to put your own figures in first, calculate part-time pro rata pay.

How is part-time pro rata pay worked out? Your pay is the full-time (FTE) salary scaled by your fraction of full time:

• By days: 3 of 5 days a week = 3/5. On $30,000 full time, that’s $30,000 × 3/5 = $18,000.
• By hours: 21 of a 35-hour week = 21/35, which is also 3/5 — the same $18,000.

The fraction is the whole story: figure out your share of full time, multiply the FTE salary by it, and that’s your pro-rata gross (before tax). Get the share right and the rest is one multiplication — the worked example below runs a real salary through it.

The Core Formula: Your Fraction of Full Time

Every part-time pro-rata calculation is the same shape: full-time salary × (your share of full time). The only real question is how to express your share.

• Days basis: if full time is 5 days and you work 3, your share is 3/5 = 0.6 (60% of full time).
• Hours basis: if full time is 37.5 hours and you work 22.5, your share is 22.5 ÷ 37.5 = 0.6 — the same 60%, just expressed in hours.

When days and hours describe the same arrangement, they agree. The reason to know which one your contract uses is that they can diverge — for example, if your three days are longer or shorter than a standard full-time day. Always scale by the basis your contract actually states, not the one that’s easiest to picture. The worked example below puts a real salary through this formula.

Worked Example: 3 Days a Week on $30,000

Take the headline case. A role advertises $30,000 full-time (pro rata) and you’ll work 3 of 5 days:

1. Find your fraction. 3 ÷ 5 = 0.6 (60% of full time).
2. Scale the salary. $30,000 × 0.6 = $18,000.
3. That $18,000 is your pro-rata gross — before tax and deductions. Your take-home will be lower, because tax comes off afterwards; this calculation stays in gross.

So the advert’s $30,000 and your $18,000 aren’t in conflict — the $30,000 is the full-time-equivalent figure, and $18,000 is your real proportion. To see the same arithmetic on your own salary and schedule, use the 3-day-a-week salary calculator at the top of this page; it shows each step so the result is never a black box.

How to Check You’re Not Being Short-Changed

Part-time pay is where small errors hide, because there’s an extra step for a mistake to creep into. A few checks catch most problems:

• Recompute from the FTE figure. Take the full-time salary, multiply by your fraction, and compare to your contract’s gross. If the contract figure is lower than your fraction implies, that’s worth a question.
• Confirm the basis. Ask whether your salary is scaled by days or by contracted hours, and make sure the fraction on your contract matches the schedule you actually work. A 3-day week scaled as if it were 2.5 days would quietly underpay you.
• Check the full-time reference is right. Your fraction depends on what “full time” means at your employer — 5 days, or 35 vs 37.5 vs 40 hours. The wrong denominator skews everything.
• Compare gross to gross. Always line up your pro-rata gross against the contract or payslip gross line, never against take-home — tax differences aren’t a short-change.

If those line up, your pro-rata pay is consistent and you’re getting your full proportion. If the contract figure comes out below your recomputed number and the basis checks out, you can put a precise figure on the question instead of a feeling: “3 of 5 days on the $30,000 full-time salary works out to $18,000; my contract shows $[X] — could you explain how that was scaled?”

When the Numbers Don’t Match

If your figure and your employer’s don’t agree, it’s usually one of three things, in order of likelihood: a different basis (days vs hours), a different full-time reference (the denominator), or a genuine calculation slip. Work through them with the calculator before assuming the worst — switch between a days and an hours basis, confirm the full-time figure, and see which combination lands on your contract’s number. If the disagreement is about a partial first month rather than your ongoing schedule, that is a different question with its own answer: which divisor your employer used to turn salary into a daily rate.

Often, the difference is explained by the calculation basis rather than an error, and the “missing” money is just the full-time figure you were never going to receive. But you don’t have to take a contract on trust — work your own figures through the prorated salary calculator, or switch to the general pro rata calculator to compare scenarios, and watch your proportion proved step by step.