Federal Self-Employment Tax (Schedule SE) Calculator

How this calculator works

Self-employment tax under IRC § 1401 is the self-employed taxpayer's combined Social Security and Medicare contribution — both the "employer half" and the "employee half" of FICA — collected through Schedule SE on Form 1040 instead of through payroll withholding. A W-2 employee splits FICA with their employer: 6.2% Social Security and 1.45% Medicare withheld from wages, with a matching 6.2% + 1.45% paid by the employer under IRC § 3101 and § 3111. A self-employed person plays BOTH roles, so SECA (the Self-Employment Contributions Act) imposes the full 12.4% + 2.9% = 15.3% on net SE earnings up to the Social Security wage base, and 2.9% only on earnings above the base (Medicare has no cap).

The mechanic the calculator surfaces is the chain of statutory adjustments that distinguishes the SE tax from a naive "15.3% of net business income" calculation: the 92.35% multiplier under § 1402(a)(12), the $400 de minimis under § 1402(b), the W-2-wage offset to the Social Security wage base under § 1402(b)(1), the Additional Medicare 0.9% layer above the filing-status threshold under § 3101(b)(2), and the above-the-line half-SE deduction under § 164(f).

The components

| Component | Rate | Base | Cap | | -------------------------------- | --------------- | ---------------------------------------------------- | ----------------------------------------- | | OASDI (Social Security) | 12.4% | Net SE earnings | $182,000 (2026 est.) — wage base | | Medicare (Hospital Insurance) | 2.9% | Net SE earnings | None (no cap) | | Additional Medicare (§ 3101(b)(2)) | 0.9% | Combined wages + SE earnings above threshold | None (no upper cap) |

The Additional Medicare thresholds are statutorily fixed and not inflation-adjusted: $200,000 for single and head-of-household, $250,000 for married filing jointly, $125,000 for married filing separately. They have not moved since the 2010 Affordable Care Act enacted them, so they catch more filers every year — the same bracket-creep design used for the NIIT thresholds under IRC § 1411.

The 92.35% multiplier

Under § 1402(a)(12), net self-employment earnings — the base on which the 12.4% and 2.9% rates run — equal net SE income times 0.9235. The multiplier synthesizes the deduction an employer would normally claim for the employer half of FICA: a regular employer pays 7.65% FICA and deducts that 7.65% as a business expense. The self-employed person is BOTH the employer and the employee, so the statute reduces the SE earnings base by 7.65% before applying the SE rate. Algebraically: (1 − 0.0765) = 0.9235. This is the single most-forgotten adjustment in DIY SE tax computations — applying the 15.3% rate directly to net SE income overstates the tax by ~7.65%.

The $400 de minimis

Under § 1402(b), if net SE earnings (after the 92.35% multiplier) for the year are less than $400, no SE tax is owed. This keeps occasional side income — a one-off freelance project, a small hobby that crosses into trade-or-business territory, a part-year consulting gig — out of the SECA system. The threshold has not been adjusted for inflation since the 1954 SECA enactment. Importantly, the de minimis covers only the SE tax (12.4% + 2.9%) — the 0.9% Additional Medicare can still apply on combined W-2 wages plus SE earnings.

Worked example 1: full-time self-employed, $80,000 net SE income

A single sole proprietor with $80,000 of net SE income (after deducting business expenses), no W-2 wages from any other job, computing for 2026.

• Net SE earnings: $80,000 × 0.9235 = $73,880
• OASDI: $73,880 × 12.4% = $9,161.12 (well below the $182,000 wage base, so applies to the full amount)
• Medicare: $73,880 × 2.9% = $2,142.52
• Schedule SE total: $11,303.64
• Half-SE deduction (Schedule 1, Line 15): $11,303.64 / 2 = $5,651.82 above-the-line
• Effective SE rate: $11,303.64 / $80,000 = 14.13% (matches 15.3% × 0.9235)
• Additional Medicare: combined earnings $73,880 are below the $200,000 single threshold — $0

Worked example 2: $200,000 net SE income — crossing the wage base

A single consultant with $200,000 of net SE income, no W-2 wages.

• Net SE earnings: $200,000 × 0.9235 = $184,700 (exceeds the $182,000 wage base)
• OASDI: capped at $182,000 × 12.4% = $22,568
• Medicare: $184,700 × 2.9% = $5,356.30 (no cap)
• Schedule SE total: $27,924.30
• Half-SE deduction: $13,962.15

Notice the OASDI cap: above the wage base, the marginal SE rate drops from 15.3% to just 2.9% (Medicare only). The next $10,000 of net SE income would cost only $268 of SE tax, not $1,530.

Worked example 3: $250,000 net SE income — Additional Medicare kicks in

The same single consultant, but with $250,000 of net SE income.

• Net SE earnings: $250,000 × 0.9235 = $230,875
• OASDI: $182,000 × 12.4% = $22,568 (capped at wage base)
• Medicare: $230,875 × 2.9% = $6,695.38
• Schedule SE total: $29,263.38
• Combined earnings (SE only — no W-2): $230,875
• Above single $200,000 Additional Medicare threshold by: $30,875
• Additional Medicare: $30,875 × 0.9% = $277.88
• Total SE + Additional Medicare: $29,541.25

Half-SE deduction is $14,631.69 — note that the Additional Medicare is NOT halved. Only the regular SE tax (12.4% + 2.9%) is deductible above-the-line.

Worked example 4: side business plus W-2 day job

A salaried professional earning $80,000 in W-2 wages and $100,000 of net SE income from consulting on the side.

• Net SE earnings: $100,000 × 0.9235 = $92,350
• Remaining SS wage base after W-2: $182,000 − $80,000 = $102,000
• OASDI base: min($92,350, $102,000) = $92,350
• OASDI: $92,350 × 12.4% = $11,451.40
• Medicare: $92,350 × 2.9% = $2,678.15
• Schedule SE total: $14,129.55

If the same filer's W-2 wages were $200,000 (above the wage base entirely), the remaining wage base would be $0 and OASDI SE tax would be $0 — the W-2 employer's withholding already exhausted the OASDI obligation. The filer would owe only Medicare ($2,678.15) and any Additional Medicare on combined earnings above $200,000 ($92,350 of SE earnings + $200,000 W-2 = $292,350; $92,350 above threshold × 0.9% = $831.15 Add'l Medicare).

The half-SE deduction (Schedule 1, Line 15)

Under IRC § 164(f), half of the Schedule SE tax (12.4% + 2.9% portions, NOT the 0.9% Additional Medicare) is an above-the-line deduction on Schedule 1, Line 15 of Form 1040. This deduction completes the FICA parallel: a regular employer deducts the employer half of FICA as a business expense, reducing the employer's taxable income; the self-employed person deducts half of the SE tax against AGI, achieving the equivalent reduction.

The deduction is above-the-line — it reduces AGI directly, without itemizing — so it benefits every self-employed filer regardless of whether they take the standard or itemized deduction. It also reduces MAGI for other calculations (NIIT threshold, IRA deductibility, premium tax credit, education credits, etc.), which can be valuable in a year close to one of those phase-outs.

§ 199A QBI interaction

Under IRC § 199A(c)(4), qualified business income for the 20% pass-through deduction is REDUCED by the half-SE deduction allocable to the qualified business. The half-SE deduction lowers AGI, but it also reduces the QBI base — partially offsetting the QBI benefit. Worked example: sole proprietor below the § 199A income threshold with $100,000 of net SE income.

• SE tax: $14,129.55. Half-SE deduction: $7,064.78 (reduces AGI).
• QBI for § 199A: $100,000 − $7,064.78 = $92,935.22
• 20% × $92,935.22 = $18,587.04 QBI deduction

Without the half-SE reduction (a common error), the QBI deduction would appear to be 20% × $100,000 = $20,000 — overstated by $1,412.96. The full § 199A computation including the income-zone thresholds, SSTB carve-out, and W-2 wage / UBIA limits runs in the companion calculator at /federal-tax/section-199a-qbi-deduction-calculator/.

Self-employed retirement plans and health insurance

These are SEPARATE above-the-line deductions that further reduce AGI for self-employed filers — but they do NOT change the SE tax computation itself. The SE tax is computed on net SE income BEFORE these adjustments.

• Self-employed health insurance (IRC § 162(l)): 100% of health insurance premiums for self, spouse, and dependents — deductible above-the-line on Schedule 1, Line 17 — provided the business has net income at least equal to the premiums and the taxpayer is not eligible for a subsidized employer plan through a spouse.

• SEP-IRA: up to 25% of net SE earnings (after the half-SE deduction — technically about 20% of net SE income), capped at $69,000 for 2025 (~$70,000+ estimated for 2026). Setup is simple; contributions are made by the tax return's extended due date.

• Solo 401(k): the same 25% employer-equivalent contribution PLUS an employee-deferral contribution of up to $23,000 ($30,500 if age 50+ for 2025) — total cap of $69,000 (same as SEP). Setup is slightly more complex but supports Roth contributions and loans.

• Defined-benefit pension plan: for older high-earning self-employed filers (age 50+ with $300K+ of SE income), a defined-benefit plan can support deductions well into six figures per year. Requires actuarial certification and annual administration.

These contributions reduce AGI dollar-for-dollar without affecting SE tax. For a high-earning self-employed filer in a peak earning year, the SEP or solo 401(k) is the single largest AGI-reduction lever available.

Common errors

• Forgetting the 92.35% multiplier — applying the 15.3% rate directly to net SE income overstates SE tax by ~7.65%.
• Forgetting that W-2 wages reduce the available SS wage base — overstates the OASDI portion when day-job wages partially fill the base.
• Forgetting that W-2 wages above the wage base eliminate the OASDI SE tax entirely — the side business still owes 2.9% Medicare but $0 OASDI.
• Confusing the Additional Medicare thresholds with the NIIT thresholds — both are $200K/$250K/$125K, but they apply to different bases (NIIT is investment income via MAGI; Add'l Medicare is wages + SE earnings — no MAGI test for Add'l Medicare).
• Halving the Additional Medicare on the Schedule 1, Line 15 deduction — only the regular SE tax (12.4% + 2.9%) is halved; the 0.9% Add'l Medicare is NOT deductible.
• Forgetting the § 199A QBI interaction — overstating the QBI deduction by ignoring the IRC § 199A(c)(4) requirement that QBI be reduced by the half-SE deduction allocable to the qualified business.
• Missing the $400 de minimis on the SE side while still owing Add'l Medicare — a high-W-2 earner with $300 of SE income still owes Add'l Medicare on the small SE earnings if combined with W-2 wages above the filing-status threshold.

How this page is maintained

The IRC § 1401 / § 1402 framework has been stable for decades, with the rates fixed in statute. The Social Security wage base updates annually per the SSA Cost-of-Living Adjustment released in October — the 2026 estimate of $182,000 reflects historical inflation-adjustment methodology and will be reconciled against the official 2026 SSA release. The 0.9% Additional Medicare thresholds are statutorily fixed and have not moved since 2010. We monitor the SSA wage base announcement and refresh the constant accordingly.

Last reviewed: 2026-05-16 against IRC § 1401; IRC § 1402; IRC § 164(f); IRC § 3101(b)(2); IRC § 199A(c)(4); IRS Form 1040 Schedule SE + instructions; IRS Form 8959; IRS Pub. 334; SSA Wage Base announcement (42 U.S.C. § 430).

Tools, not advice — this calculator is a planning tool. Consult a qualified tax professional before relying on a result for return preparation or any other action.