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.

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.