Deorbit Plan

Social Security tax calculator: how much of your benefit is taxable

Provisional income, the 0%, 50% and 85% zones, and the tax on your next dollar

By the Deorbit Plan editorial team, a Berrydyne program · Last reviewed · Topic: Social Security

What it computes

Up to 85% of Social Security benefits can be taxable income. How much depends on your provisional income: other income plus tax-exempt interest plus half your benefits[3]. Below $32,000 ($25,000 for single and head-of-household filers) none of the benefits are taxable; up to $44,000 ($34,000) up to 50% are; above that up to 85%[1]. This calculator runs that worksheet (with the same code the simulator uses) and then the 2026 federal brackets, so you can see what one more dollar of income really costs while benefits are being pulled into tax.

How much of your Social Security is taxable?

Provisional income is $52,000, so $12,800 of your $40,000 in benefits (32%) is taxable. You are in the 85% zone: each extra dollar makes 85 cents of benefits taxable. The next $100 of other income would cost about $19 in federal tax: a 18.5% rate, not the 10% bracket rate.

  • Up to $32,000: none taxable
  • $32,000 – $44,000: up to 50%
  • Above $44,000: up to 85%
  • 85% of benefits taxable (cap)
  • Provisional income: $52,000 = other income $30,000 + tax-exempt interest $2,000 + half of benefits $20,000.
  • Taxable benefits: $12,800 (32% of benefits); $27,200 stays tax-free.
  • Next dollar: each extra $100 of other income makes $85 more of your benefits taxable; the federal tax on that $100 is 18.5% (bracket rate 10%).
  • Federal income tax on all of it: $1,060 (married filing jointly, standard deduction, no age-65 extras).

The base amounts are fixed in the tax code and not adjusted for inflation.

Worked example

A married couple receives $40,000 of Social Security, draws $30,000 from IRAs and earns $2,000 of municipal-bond interest. Provisional income is $30,000 + $2,000 + $20,000 = $52,000, above the $44,000 second threshold, so $12,800 of benefits (32%) is taxable.

Their bracket rate is 10%, but each extra $100 they withdraw also makes $85 more of their benefits taxable, so the next $100 costs $19: an effective 18.5% rate. Note the tax-exempt interest: it is not taxed itself, yet it raised provisional income and with it the taxable share of benefits.

What it ignores

  • State income tax (most states do not tax Social Security at all).
  • The age-65 additional standard deduction and the temporary senior deduction. The marginal-rate map includes them.
  • How other income is split between ordinary income and capital gains: everything is taxed as ordinary income here.
  • Lump-sum payments for earlier years, repaid benefits, and the separate rule for a married person filing separately who lived apart all year.
  • Medicare premiums withheld from benefits (the gross benefit is what counts).

The rule behind it

The full explanation, with sources, is in The Social Security tax torpedo.

See it over a full plan

Taxable benefits change every year as withdrawals, RMDs and conversions change. The simulator runs this worksheet in every year of a plan, and its Lab sweeps claiming ages to show how the torpedo moves. Open it in the simulator →

If you already have a saved plan, the link only takes you to the right panel; your plan is not changed.

Embed this tool on your site

Paste this HTML where the tool should appear. It keeps the credit link visible, shows no ads, and reads nothing stored on your visitors’ devices; what they type stays in their browser.

Optional: add this script once on the page and each embedded tool grows to fit its content instead of scrolling inside the frame.

This tool shows how the rules work. It is not financial, tax or investment advice. See the disclaimer.

Sources