Under a rolling FMLA 12-month period, your employer counts backward 12 months from the day you want to take leave, adds up the FMLA time you already used inside that window, and subtracts it from 12 weeks. Whatever is left is what you can take. There is no fixed reset date, so your available balance shifts every day.
How the Backward Count Works
Every FMLA request triggers its own calculation. Your employer picks the date your new leave would start, looks back exactly 12 months from that date, and tallies every hour of FMLA leave that falls inside that window. Your entitlement is 12 workweeks minus that tally.1U.S. Department of Labor. Fact Sheet #28H: 12-month Period under the Family and Medical Leave Act
A worked example makes it concrete. Say you want leave to start November 1, 2025. Your employer looks back to November 2, 2024. Inside that window, you took four weeks starting January 1, 2025, another four weeks starting March 1, 2025, and three weeks starting June 1, 2025. That is 11 weeks used. You have one week available as of November 1.1U.S. Department of Labor. Fact Sheet #28H: 12-month Period under the Family and Medical Leave Act
A quieter year looks very different. If you took two weeks starting April 15, 2025 and need leave again on September 1, 2025, the lookback runs from September 2, 2024 through September 1, 2025. Those two April weeks sit inside that window, so you have 10 weeks left. Wait until May 1, 2026 with no FMLA use in between, and the April 2025 leave has aged out entirely. You have the full 12 weeks again.
How Used Leave Rolls Off
This is where the rolling method surprises people. Prior leave does not disappear all at once. It drops off the count day by day as those older dates fall outside the 12-month lookback.2eCFR. 29 CFR 825.200 – Amount of Leave
Return to the earlier example. You had one week left on November 1, 2025 and you use it. You are not entitled to any new FMLA leave until January 1, 2026, when the four weeks you took in January 2025 begin to age out of the window. From that date forward, you regain one day of FMLA leave for each day that passes, matching the pace at which you originally used the leave a year earlier.
The practical consequence is that you can fall in and out of FMLA protection during stretches when your balance is low. If you need six continuous weeks but only four are available because the rest has not rolled off yet, FMLA covers only the first four. The last two weeks are unprotected unless your employer voluntarily extends coverage or a state law reaches further.
Intermittent Leave and Partial Weeks
FMLA leave does not have to run in one block. Recurring treatments, chronic conditions that flare up, and reduced schedules can all be taken as intermittent leave. Under the rolling method, every one of those absences triggers its own lookback, so your balance can shift week to week.
Partial weeks are charged proportionally. If you normally work 40 hours and take a single eight-hour day, that is one-fifth of a week of FMLA leave. Drop to a four-hour daily schedule for a full week and you have used half a week.3eCFR. 29 CFR 825.205 – Increments of FMLA Leave for Intermittent or Reduced Schedule Leave
The smallest increment your employer can use to track FMLA leave is no larger than the shortest increment they use for any other type of leave, and it can never exceed one hour. If sick leave is tracked in 15-minute blocks, FMLA can be too. Your employer cannot round you up to a full day for a 90-minute appointment.4eCFR. 29 CFR 825.205 – Increments of FMLA Leave for Intermittent or Reduced Schedule Leave
Why Employers Choose This Method
Federal regulations give employers four ways to define the 12-month FMLA period: the calendar year, any fixed 12-month period such as a fiscal year, a forward-looking period that starts on your first day of leave, or the rolling method measured backward.2eCFR. 29 CFR 825.200 – Amount of Leave Whichever one they pick has to apply to every employee the same way.1U.S. Department of Labor. Fact Sheet #28H: 12-month Period under the Family and Medical Leave Act
The first three methods create a predictable reset date, which also creates a stacking opportunity. Someone on the calendar year could take 12 weeks in October, November, and December, then take another 12 weeks starting January 1, for 24 consecutive weeks of protected leave. The rolling method eliminates that. Because it always looks back from today, you can never have more than 12 weeks of FMLA leave in any 12-month span, no matter how you time it.
If Your Employer Changes Methods
An employer that wants to switch from one calculation method to another has to give employees at least 60 days’ notice. During that transition, whichever method gives you more leave is the one that applies to you.1U.S. Department of Labor. Fact Sheet #28H: 12-month Period under the Family and Medical Leave Act The same tiebreaker protects you if your employer never formally chose a method: the calculation that produces the more favorable outcome governs your leave.5U.S. Department of Labor. Family and Medical Leave Act Advisor – Selecting a 12-Month Leave Year
Tracking Your Own Balance
The rolling method asks more of you than the others. There is no January 1 that wipes the slate, and every request forces a fresh calculation. If you expect to need FMLA more than once in a year, keep a simple log: the exact start and end dates of every FMLA absence, the hours charged, and whether the leave was continuous or intermittent. HR can confirm your current balance, but your own records prevent disputes.
Your employer is required to tell you which 12-month period applies to your entitlement. When they issue the notice designating your leave as FMLA, that notice has to identify the applicable period.6eCFR. 29 CFR 825.300 – Employer Notice Requirements If you cannot get a straight answer about which method your employer uses, put the question to HR in writing. An employer that fails to meet its notice obligations can be liable for benefits or compensation you lost as a result.
Situations the Rolling Method Does Not Cover the Same Way
Military caregiver leave runs on its own clock. If you are caring for a covered servicemember or recent veteran with a serious injury or illness, you get up to 26 workweeks in a single 12-month period that starts the first day you take that leave and runs forward, regardless of whether your employer otherwise uses the rolling method for standard FMLA.7eCFR. 29 CFR 825.127 – Leave to Care for a Covered Servicemember with a Serious Injury or Illness Any unused portion of those 26 weeks is forfeited when that single period ends. It does not roll off.
Spouses who work for the same employer share a combined 12 weeks for the birth or placement of a child and for caring for a parent with a serious health condition. Each spouse still gets a full independent 12 weeks for their own serious health condition, to care for a spouse or child with a serious condition, or for qualifying military exigency leave. Under the rolling method, each spouse’s balance is calculated separately from their own leave history.8U.S. Department of Labor. Fact Sheet #28L: Leave under the Family and Medical Leave Act When You and Your Spouse Work for the Same Employer
Finally, the federal 12 weeks is a floor. Several states run their own family and medical leave programs with longer entitlements, paid wage replacement, or broader coverage. Where a state law applies, your employer generally has to comply with both, and you get the benefit of whichever rule is more generous on any given provision.