An FSA contribution comes out of pay before income tax, the same pre-tax mechanic this site’s HSA calculator covers — the immediate benefit is the tax saved on the contribution.
How it works
The annual contribution multiplied by a marginal tax rate gives the tax saved; subtracting that from the contribution gives its real net cost.
Why “use it or lose it” matters here
Unused FSA funds are generally forfeited at year-end, aside from a limited carryover some employers allow (up to $680 for 2026) or a short grace period — unlike an HSA, which has no such deadline. Contributing more than what will realistically be spent on eligible expenses risks losing the unused portion entirely, which this calculator’s tax-savings figure doesn’t account for.
How to use this calculator
- Enter the planned annual FSA contribution, up to the 2026 limit of $3,400.
- Enter a marginal tax rate.
Frequently asked questions
Does an FSA also save on payroll tax?
Yes, typically — FSA contributions usually also avoid Social Security and Medicare tax, an additional saving not reflected in this calculator’s tax-rate-only estimate.
What happens to unused FSA money?
Generally forfeited at year-end, unless the employer offers a limited carryover or grace period — planning contributions close to expected annual eligible expenses avoids losing money to this rule.
Can I change my FSA contribution mid-year?
Usually only after a qualifying life event, unlike an HSA, which can typically be adjusted at any time.
