FSA calculator: how much to put in your flexible spending account

List the medical costs you expect next year and how sure you are of each. See the tax you'd save and what you could forfeit under use-it-or-lose-it, for four different elections, whether fewer or more of those costs happen.

✓ TestedSame calculation as the tested spreadsheet

Suggested election (certain + likely costs)–

Certain costs
Likely costs
Maybe costs

Net benefit = tax saved − money forfeited, by what actually happens

Elect

Certain happen

+ likely

All

Tax saved = election × your tax rate. The FSA pays the costs that happen, up to your election; what's left over is carried to next year up to your plan's carryover (enter 0 if it has none) and the rest is forfeited. 2026: $3,400 limit, $680 maximum carryover. Grace periods aren't modelled. The spreadsheet adds a year-long expense log and claim tracking.

How it works

Money you put in a health FSA comes out of your pay before tax, so every dollar you elect saves your tax rate on it, but only if you spend it: what is left at the end of the plan year is forfeited, apart from any carryover your plan allows. The calculator adds up your expected costs in three groups, certain, likely and maybe, and tries four elections against three outcomes. In the example, electing the certain and likely costs, $1,490, saves $447 of tax; if only the certain costs happen, $690 is left, $680 carries over and $10 is lost. Electing the $3,400 limit would lose $900 in the same year.