HSA vs FSA Calculator

About this calculator

This calculator compares the effective net cost of putting money into a Health Savings Account (HSA) versus a Flexible Spending Account (FSA) for the same medical expenses. Both reduce your taxable income by the contribution amount, but they differ in what happens to unused funds: HSA balances roll over indefinitely and stay yours even if you change jobs, while most FSAs are subject to a use-it-or-lose-it rule (with only a small carryover or grace period allowed by the IRS), so unspent FSA money is typically forfeited.

US employees choosing between benefits during open enrollment use this comparison to see past the identical up-front tax savings and into the real difference: an HSA (only available with a qualifying High-Deductible Health Plan) has more long-term value if spending is unpredictable, since nothing is lost, while an FSA can still make sense for known, predictable annual expenses like orthodontia or a stable prescription. Benefits advisors and HR teams reference this same forfeiture-risk logic when explaining plan options to employees.

This calculator takes your expected contribution, tax rate, and the estimated chance of forfeiting unused FSA funds, then returns the effective net cost of each account so you can see which one actually saves you more.