HSA paycheck calculator
Enter your salary and the HSA contribution you route through your employer's cafeteria plan (Section 125) salary reduction. You get per-paycheck take-home, the federal income tax change, and the Social Security and Medicare tax change. 2026 federal HSA limits are built in.
An HSA contribution through a cafeteria plan is exempt from federal income tax withholding, Social Security tax and Medicare tax up to the 2026 limits of $4,400 self-only and $8,750 family. At $65,000 a year, biweekly, single, $100 a paycheck changes take-home from $2,093 to $2,012.
Updated 2026-10-29
Method. Federal income tax withholding uses the IRS Publication 15-T (2026) percentage method for a 2020 or later Form W-4, single, with no other entries. Social Security tax is 6.2% up to the $184,500 wage base. Medicare tax is 1.45%, plus 0.9% on wages above $200,000. The HSA amount comes out of the wages for all three taxes. The result is an estimate, not tax advice.
The calculator
| Line | No HSA | With HSA |
|---|---|---|
| Federal income tax / yr | ||
| Social Security tax / yr | ||
| Medicare tax / yr | ||
| Take-home pay / yr | ||
| Your HSA payroll contribution / yr | $0 | |
| Take-home + your contribution / yr |
Social Security and Medicare tax saved by the cafeteria plan route: $199 a year.
If you pay into an HSA yourself, IRS Publication 969 (2025) says: "You can claim a tax deduction for contributions you or someone other than your employer make to your HSA even if you don't itemize your deductions on Schedule A (Form 1040)." The cafeteria plan route also takes the amount out of Social Security and Medicare wages.
2026 limits: $4,400 self-only, $8,750 family ($5,400 / $9,750 if you are 55+). The tool adds your yearly amount and the employer amount and compares the total with the limit.
Contribution ladder at the default salary
Each row holds a different per-paycheck HSA amount through the plan at $65,000, biweekly, single, federal taxes only.
| Per paycheck | Annual HSA | Take-home drop | Saving rate |
|---|---|---|---|
| $50 | $1,300 | $40 | 19.65% |
| $100 | $2,600 | $80 | 19.65% |
| $150 | $3,900 | $121 | 19.65% |
The saving rate is (federal income tax withholding saved + Social Security and Medicare tax saved) / contribution.
Why the cafeteria plan route matters
An HSA contribution through your employer's cafeteria plan (section 125) is treated as an employer contribution. Up to the 2026 limits, it is exempt from federal income tax withholding, Social Security tax and Medicare tax. On a $65,000 salary with $2,600 a year into the HSA, this example saves $312 of federal income tax withholding and $199 of Social Security and Medicare tax.
Employer and employee HSA contributions made this way are reported on Form W-2, box 12, code W. Employee Social Security tax is 6.2% on wages up to the $184,500 wage base. Medicare tax is 1.45% with no wage base limit. Below the wage base, the plan route saves 7.65 cents of these taxes on each dollar. Above the wage base, it saves only the Medicare part.
Age 55 catch-up. IRS Publication 15-B (2026): "The contribution amounts listed above are increased by $1,000 for a qualified individual who is age 55 or older at any time during the year." The tool adds $1,000 to the limit when you select age 55 or older.
What the IRS publications say
IRS Publication 15-B (2026), section Health Savings Accounts (HSAs): "Up to specified dollar limits, cash contributions to the HSA of a qualified individual (determined monthly) are exempt from federal income tax withholding, social security tax, Medicare tax, and FUTA tax if you reasonably believe that the employee can exclude the benefits from gross income."
The same section, paragraph Cafeteria plans: "You may contribute to an employee's HSA using a cafeteria plan". IRS Publication 969 (2025): "Contributions to an employee's account by an employer using the amount of an employee's salary reduction through a cafeteria plan are treated as employer contributions."
Form W-2. IRS Publication 15-B (2026): "You must report your contributions to an employee's HSA in box 12 of Form W-2 using code W." Publication 969 (2025) says that this includes "amounts the employee elected to contribute through a cafeteria plan".
Sources
- IRS, Publication 15-B (2026), Employer's Tax Guide to Fringe Benefits, section Health Savings Accounts (HSAs).
- IRS, Rev. Proc. 2025-19, section 2.01, 2026 HSA contribution limits.
- IRS, Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans.
- IRS, Publication 15 (2026), (Circular E), Employer's Tax Guide.
- IRS, Publication 15-T (2026), Federal Income Tax Withholding Methods.
- IRS, Topic no. 751, Social Security and Medicare withholding rates.
What this tool does not model
- State income tax. Some states tax HSA contributions. Check your state rules. California does not exclude employer and cafeteria-plan HSA contributions from state wages (California Franchise Tax Board, 2025 Instructions for Schedule CA (540), line 1h, and 2025 FTB Publication 1001).
- The last-month rule and mid-year contribution changes are out of scope.
- Investment earnings inside the HSA.
Method and limitations
The HSA amount comes out of the wages for federal income tax withholding, Social Security tax and Medicare tax, so take-home drops by the contribution minus the tax saved. Filing status is single and the same amount is paid each pay period. Michael maintains StateWage. He is not a CPA, an attorney or a payroll provider. The result is an estimate, not tax advice.