HSA Contribution Calculator

Per Pub 969, you are an eligible individual for a given month if, on the first day of that month, all four of these are true:

• You are covered by an HDHP.For 2026 that means a deductible of at least $1,700 (self-only) or $3,400 (family) and an out-of-pocket cap no higher than $8,500 / $17,000. Plan names like "HSA-eligible" or "HDHP" usually confirm it, but check the deductible.
• You have no other disqualifying coverage.A spouse's traditional PPO that covers you, a general-purpose health FSA (yours or your spouse's), or a health reimbursement arrangement that pays before the deductible all disqualify you. Dental, vision, and limited-purpose FSAs are fine.
• You are not enrolled in Medicare. Enrolling in any part of Medicare, including Part A that starts automatically with Social Security benefits, ends eligibility from that month. Contributions must be prorated for the months before enrollment.
• Nobody can claim you as a dependent.

Self-employed owners qualify on the same terms: buy an HDHP on the individual market (or through a spouse's employer) and you can fund an HSA directly. Sole proprietors, partners, and more-than-2% S corporation shareholders cannot run contributions through a Section 125 payroll plan, which is why the "direct deposit" option in the calculator shows no FICA saving. See how the self-employed health insurance deduction stacks with the HSA deduction.

If you were not eligible all year, Pub 969's limitation chart gives you 1/12 of the annual limit (including any catch-up) for each month you were eligible on the 1st. Coverage that starts May 1, 2026 on a self-only plan counts 8 months: $4,400 × 8/12 = $2,933.33. Coverage that starts May 15 still counts only June through December, or 7 months, because May 1 was missed.

The last-month rule overrides the chart: if you are eligible on December 1, the IRS treats you as eligible for the whole year, so the same person could contribute the full $4,400. The catch is the testing period, which runs from December 2026 through December 31, 2027. Lose HDHP coverage in that window (for any reason other than death or disability) and the amount you could not have contributed under the chart, here $1,466.67, is added to your income for 2027 plus a 10% additional tax ($146.67).

Practical rule: use the last-month rule only if you are confident you will keep an HDHP through the end of next year. If you are job-hunting, planning a move to a spouse's plan, or turning 65 soon, contribute the prorated amount. The calculator shows both numbers when the toggle is on.

The same monthly logic applies to Medicare. Someone who enrolls in Medicare on September 1, 2026 has 8 eligible months (January through August), and Social Security can backdate Part A up to six months, so many people stop contributing six months before they apply.

An HSA is the only account that is tax-free on the way in, while it grows, and on the way out. That is why financial planners often say to max the HSA before a traditional IRA once any 401(k) match is captured.

Sources: Rev. Proc. 2025-19 (HSA), Rev. Proc. 2025-32 (health FSA), IRS Notice 2025-67 (IRA), all verified September 2026. Compare the retirement side with the Roth IRA calculator or, if you are self-employed, the Solo 401(k) calculator.

Reporting. Every HSA owner files Form 8889 with their 1040. Part I totals contributions (yours and your employer's, which show up in Box 12 code W of a W-2) and computes the deduction, which goes to Schedule 1, line 13. Part II reports distributions from Form 1099-SA; your custodian also sends Form 5498-SA. Our guides to Form 8889 and Form 5498-SA walk through each line.

Self-employed specifics. Your HSA deduction is above the line, so it reduces AGI and can help with income-based phase-outs, but it does not reduce net earnings from self-employment. A sole proprietor at a 22% federal rate who contributes $4,400 saves $968 federally and nothing on the 15.3% self-employment tax. Estimate that separately with the self-employment tax calculator. Because there is no payroll, contribute directly to the HSA custodian any time up to the April 15 deadline, and remember that only the months you actually held an HDHP count.

What you can spend it on. Qualified medical expenses follow IRS Publication 502: deductibles, copays, prescriptions, dental and orthodontic work, vision care and glasses, hearing aids, mental health care, acupuncture, chiropractic care, and over-the-counter medicines and menstrual products. Insurance premiums are generally not qualified, with four exceptions: COBRA, coverage while receiving unemployment, Medicare premiums (Parts B, D, and Advantage, but not Medigap) once you are 65, and qualified long-term care insurance up to age-based limits.

After 65. You can no longer contribute once you enroll in Medicare, but the account keeps working. Medical withdrawals stay tax-free, and non-medical withdrawals are taxed as ordinary income with no 20% additional tax, which makes an HSA behave like a traditional IRA with a medical bonus. Keeping receipts for expenses you paid out of pocket in earlier years lets you reimburse yourself tax-free at any later date.