How PTO Accrual Actually Works

Most people know their paid time off balance today and have no idea what it will be in April — which is a problem, because April is when the leave request goes in. Payroll portals show the current number and almost never project forward.

PTO accrual is simple arithmetic once you know which of three systems your employer uses. The complication is that the same headline allowance — "three weeks" — produces different balances depending on the basis, and that a cap can quietly stop you earning without anything appearing on your payslip.

No federal law requires any of this

Worth stating plainly: the United States mandates no paid vacation at all. There is no federal minimum. Paid time off exists because an employer offers it or a collective agreement requires it, which is why policies vary so wildly between companies in the same industry.

Federal law enters in only one place — the Fair Labor Standards Act governs how paid leave interacts with overtime for non-exempt workers. State law enters in another: several states treat accrued vacation as earned wages that must be paid out when you leave. Almost everything else is policy.

The three accrual bases

Per pay period. A fixed number of hours each payroll run, regardless of hours worked. Three weeks a year on a biweekly schedule is 120 ÷ 26 = 4.62 hours per period. Predictable, and the usual arrangement for salaried staff.

Per hour worked. You earn a fraction of an hour for each hour on the clock. A common formulation is 0.0577 hours per hour worked, which produces 120 hours across a 2,080-hour year. The consequence catches people out: a short week earns less, and unpaid leave earns nothing. Typical for hourly roles.

Annual grant. The entire allowance appears at once, usually on a hire anniversary or 1 January. Generous in January; awkward if you leave in March, because employers commonly prorate or claw back the unearned portion.

The 2,080-hour figure underpinning these conversions carries the same caveats discussed in the 2,080-hour rule — it assumes a full year of full weeks.

Doing the projection

The arithmetic per basis:

per pay period:  accrued = rate × periods remaining
per hour worked: accrued = rate × hours per week × weeks remaining
annual grant:    accrued = rate × (periods remaining ÷ periods per year)

Then:

projected balance = current balance + accrued − time off already booked

Someone with 40 hours banked, accruing 4 hours per period, with 13 periods left before the date they care about, will have 92 hours — about 11.5 days at an 8-hour day. The PTO accrual calculator runs all three bases and handles the cap.

One detail matters: subtract leave you have booked but not yet taken. Payroll balances typically do not deduct it until the day arrives, which makes the number on your payslip flattering.

Accrual caps are where hours vanish

A cap is a ceiling on your balance — often 1.5 or 2 times the annual allowance. Reach it and you stop accruing. You do not lose what you have; you simply stop earning more.

This is a slow and genuinely invisible cost. Someone earning 120 hours a year against a 180-hour cap, who reliably takes only a week, stops accruing partway through the year and never notices, because the balance still looks healthy. The hours are not deducted — they are never credited in the first place.

A cap is different from use-it-or-lose-it, which zeroes some or all of the balance on a fixed date. A few states restrict use-it-or-lose-it policies on the grounds that accrued vacation is earned wages; most do not. If your policy has a hard forfeiture date, work backwards from it and book something.

What the projection cannot know

Several policy details sit outside the arithmetic:

• Waiting periods. Many employers withhold accrual, or the right to use it, for the first 90 days.
• Tenure tiers. Allowances commonly step up at three, five and ten years. If yours increases mid-year, project the two stretches separately.
• Separate sick banks. Where sick leave is tracked apart from vacation — including under state and city paid-sick-leave mandates — the two accrue independently.
• Company holidays. These are usually not drawn from PTO, so do not subtract them.
• Approval. An available balance is not an approved absence. Blackout periods and staffing minimums are real constraints no calculator can model.

Payout when you leave

This is the one area where state law does serious work, and it is worth knowing before you resign. Some states — California among the strictest — treat accrued vacation as earned wages that must be paid out at separation and prohibit forfeiture. Others let a written policy say otherwise entirely.

Because it turns on your state and your policy language together, check your state labor department rather than relying on what a colleague told you. The difference on a large accrued balance can run into thousands of dollars.

Making the number useful

Project to a specific date you care about rather than to year end — the week of a wedding, the school holidays — and count the pay periods between now and then. That turns an abstract balance into an answer about whether the trip works.

If your time off will be unpaid rather than accrued, the income side matters more than the balance: the take-home pay calculator shows what a missing week costs after deductions, and the overtime pay calculator covers the other direction, where extra hours are worth one and a half times.

For the federal position on leave and the FLSA, the Department of Labor states it directly, and the Bureau of Labor Statistics publishes what leave benefits actually look like across US employers — useful context for judging whether an offer is competitive.