How Much of Your Social Security Is Taxable?
Up to 85% of Social Security benefits can be taxed federally, and the share depends on a "combined income" test whose thresholds have not moved since 1993. This calculator runs the IRS Publication 915 worksheet on your numbers, shows the federal tax that results, and - the part most calculators skip - shows what each additional IRA withdrawal does to your marginal rate as more of your benefits are pulled into taxable income.
Your numbers
Result
The worksheet, line by line
What one more IRA withdrawal does
Each row adds another $2,000 of traditional IRA or 401(k) withdrawals to what you entered. The marginal rate is the extra federal tax divided by the extra $2,000. When more of your benefits become taxable at the same time, the rate is higher than your bracket - that is the effect people call the Social Security tax torpedo.
| Extra withdrawal | Taxable benefits | Newly taxed benefits | Federal tax | Marginal rate |
|---|
How the taxable amount is decided
Combined income (the IRS also calls it provisional income) is your other income plus tax-exempt interest plus one half of your benefits. Compare it with two thresholds that depend on filing status: $25,000 and $34,000 for single filers, $32,000 and $44,000 for joint returns. Below the first threshold no benefits are taxed. Between the two, up to 50% of the excess over the first threshold is taxed (never more than half the benefits). Above the second, 85% of the excess over it is added, and the total is capped at 85% of the benefits. The thresholds are fixed in law and are not indexed for inflation, which is why a larger share of retirees pays tax on benefits every year.
The 2025 legislation added a $6,000 deduction per person aged 65 and older for tax years 2025 through 2028. It does not change how much of your benefits is taxable; it reduces taxable income afterward, and it phases out at 6% of modified AGI over $75,000 (single) or $150,000 (joint). Both effects are in the tax figure above.
What the tool assumes
- Federal only. State tax is a separate question - see Retirement Tax by State for the eight states that tax benefits.
- Standard deduction, with the aged add-on and the senior deduction where age allows. No itemized deductions, dependents, or credits.
- Other income is taxed as ordinary income. Qualified dividends and long-term capital gains actually face lower rates, so the tax figure is an upper estimate if those are large.
- Single and married filing jointly. Head of household uses the single thresholds for benefits but different brackets; married filing separately (living together) has a $0 threshold. Neither is modeled.
- Lump-sum benefits for earlier years, repayments, and the workers' compensation offset are not modeled.
Parameters used, with sources
Loaded from the same file the calculation reads.
Test cases
Each case was computed independently by a reference implementation and by this page's code; the two must agree before publication. The self-test reruns that comparison in your browser, including every row of the withdrawal ladder.
Sources
- IRS, Publication 915, Social Security and Equivalent Railroad Retirement Benefits, Worksheet 1.
- IRS, Rev. Proc. 2025-32 (2026 rate tables and standard deduction; 2025 standard deduction as amended) and Rev. Proc. 2024-40 (2025 rate tables).
- Internal Revenue Code Section 86 (taxation of benefits) and Section 151(d)(5) (senior deduction), as added by Public Law 119-21.
Corrections
If a rule or a figure is wrong, tell us. We fix it, update the checked date, and note the change here.
This tool shows what published tax rules do to the numbers you enter. It is not tax, legal or financial advice, and it does not know your situation. For a decision that matters, take the numbers to a professional who is licensed to advise you.