How PTO Accrual Works

Most paid time off doesn’t show up in your bank all at once on January 1. It builds up gradually, a little bit with every paycheck, which is why the number on your pay stub keeps shifting even if you haven’t taken a day off in months. Once you know the handful of numbers behind that math, projecting your balance for any future date is a quick calculation, not a guessing game.

How accrual works

Most employers use per-pay-period accrual: you earn a fixed number of PTO hours every time you get paid, rather than receiving your full annual allotment in one lump sum. A common example is 3.08 hours per biweekly pay period, which works out to roughly 10 vacation days a year once you multiply it across 26 pay periods.

To figure out where your balance will land on a future date, you need four things: your current balance, your accrual rate per pay period, how many pay periods remain between now and that date, and any PTO you already know you’re going to use before then. Add the accrual you’ll earn to what you already have, then subtract what you plan to spend, and you’re left with a projected balance.

This approach assumes accrual keeps running smoothly between now and your target date. It doesn’t account for anything that changes the rate itself, like a raise in accrual tied to tenure, or a policy that pauses accrual once your balance hits a cap. More on that below.

The formula

Accrued PTO        = Accrual Rate x Pay Periods Remaining
Projected Balance  = Current Balance + Accrued PTO - Hours Planned to Use

The first line tells you how much new PTO you’ll earn between now and the date you care about. The second line combines that with what you’re starting from and what you already know you’ll spend, to give you a single number: your projected balance on that future date.

Worked examples

Say you currently have 40 hours of PTO banked, you accrue 3.08 hours every pay period, there are 10 pay periods left until the date you’re planning around, and you already know you’ll use 16 hours before then (maybe a long weekend and a few scattered days):

• Accrued PTO: 3.08 hrs x 10 = 30.8 hrs
• Projected balance: 40 + 30.8 - 16 = 54.8 hrs

That’s the same result you’d get by running those inputs through the PTO Calculator: a projected balance of 54.8 hours, with 30.8 hours of that coming from accrual between now and then.

Now take a different case. Say you’re starting from a balance of 0 hours (maybe you just started a new job or came back from an unpaid leave that reset your accrual), you earn 6.67 hours per pay period, there are 6 pay periods remaining, and you don’t have anything planned to use yet:

• Accrued PTO: 6.67 hrs x 6 = 40.02 hrs
• Projected balance: 0 + 40.02 - 0 = 40.02 hrs

Because there’s no starting balance and nothing planned to subtract, the projected balance here is just the accrued amount. It’s a useful reminder that the formula doesn’t change based on your situation, only the numbers you plug into it do.

A note on caps and “use it or lose it” policies

The formula above assumes your PTO accrues continuously and without limit between now and your target date. In practice, a lot of employers cap how much PTO you can bank at once. Once you hit that ceiling, accrual simply stops until you use some PTO and drop back below the cap; it doesn’t keep piling up in the background waiting to be added later.

Some employers go further with “use it or lose it” policies that forfeit unused PTO at year-end or on your work anniversary, regardless of whether you were ever near a cap. Neither of these policies is reflected in the projection above, so if your employer has a cap or a forfeiture rule, treat the calculated number as an upper bound and check your handbook for the actual ceiling that applies to you.

It’s also worth checking whether your accrual rate itself changes over time. Many employers increase the per-period rate after a tenure milestone, like moving from 3.08 hours to 4.62 hours per period after five years. If a milestone like that falls within your projection window, split the calculation into two stretches (before and after the rate change) rather than running one long calculation at the old rate.

FAQ

Where do I find my accrual rate? Check a recent pay stub for a PTO or leave accrual line, or look in your employee handbook. If you only know your total annual PTO days rather than a per-pay-period rate, convert that into a per-period number first (for example, by dividing your annual hours by the number of pay periods in a year) before using it here.

Does this account for PTO caps or “use it or lose it” policies? No. This calculation assumes uncapped, continuous accrual between now and your target date. If your employer stops accrual once you hit a cap, or forfeits unused PTO at year-end, your actual balance could end up lower than the projection. Check your policy for any caps that might apply before relying on the number.

What if my accrual rate changes partway through the period I’m projecting? Run the calculation in two stretches instead of one. Use the old rate for the pay periods before the change and the new rate for the pay periods after it, then add the two accrued amounts together along with your starting balance and anything you plan to use, rather than applying a single rate across the whole span.

Use the PTO Calculator to run your own numbers.