Self Employment Tax Calculator – 15.3% SE, Half Deduction & Total Estimator

What Is Self Employment Tax and Why Do Freelancers Pay Both Sides?

When you are an employee, you pay 7.65% FICA and employer pays 7.65%. When you are self employed, you are both. So you pay 15.3% self employment tax — 12.4% Social Security and 2.9% Medicare — on 92.35% of net business income. Example: $75,000 net business income ×92.35% = $69,262.50 SE base. SS $69,262.50×12.4% = $8,588.55 up to wage base, Medicare $69,262.50×2.9% = $2,008.61, SE tax $10,597.16. Half $5,298.58 is deductible for income tax.

That is only SE tax. You also pay federal income tax on net minus half SE deduction minus standard deduction, and state income tax. Many new freelancers forget that total is SE + federal + state. This calculator shows all three with clear breakdown and wage base handling, not just 15.3% flat.

How To Use This Self Employment Tool — 4 Quick Steps

Step 1 — Enter net business income. Net after business expenses from Schedule C, before SE tax. Example $75,000.

Step 2 — Add other W-2 wages if any. If you also have W-2 wages $0 example, SS base is reduced. Wage base $176,100 combined W-2 and SE base subject to 12.4% SS. If W-2 $100k, only $76,100 of SE base gets SS tax, rest only Medicare.

Step 3 — Choose filing status and state. Filing status changes additional Medicare threshold $200k single $250k joint $125k separate. State for total tax view — Texas 0% no tax, California 1% to 12.3% progressive, Illinois flat 4.95%.

Step 4 — Calculate. Hit Calculate SE Tax. See SE base 92.35%, SS tax, Medicare tax, SE tax, half deduction, federal taxable after half and standard deduction, federal estimate, total tax SE+fed+state. Change W-2 wages from $0 to $100k and see SS tax drop.

How It Calculates — Formula & Methodology

Source: IRS Schedule SE, IRS Publication 334, IRS Rev Proc 2024-40 for federal brackets and standard deduction, SSA wage base.

SE Base = Net × 92.35%
SS Taxable = Min(SE Base, WageBase $176,100 - W2 Wages)
SS Tax = SS Taxable × 12.4%
Medicare Base = SE Base
Medicare Tax = Medicare Base × 2.9% + 0.9% over $200k single / $250k joint
SE Tax = SS Tax + Medicare Tax
Half Deduction = SE Tax / 2
Taxable Federal = Max(0, Net - HalfDeduction - StdDeduction - Retirement)
Federal Tax = Σ BracketSlice × Rate

Verification with $75k net single $0 W-2 $0 retirement California:

• SE Base $75k×92.35% = $69,262.50
• SS Taxable $69,262.50 (since W-2 $0, base below $176,100) ×12.4% = $8,588.55
• Medicare $69,262.50×2.9% = $2,008.61, no additional 0.9% since under $200k threshold
• SE Tax $10,597.16, Half $5,298.58
• Taxable federal $75k - $5,298.58 - $15,000 std = $54,701.42, federal brackets single: $11,925×10%=$1,192.50 + $36,550×12%=$4,386 + $6,226.42×22%=$1,369.81 total $6,948.31
• Total tax SE $10,597 + Federal $6,948 + State CA ~$2,500 = ~$20,045

Guards: floor 0, wage base $176,100, retirement 0-50% capped, threshold $200k/$250k/$125k, non-finite→0.

What Results Mean — Only Necessary Details

SE Base 92.35%: Net ×92.35% as per IRS. Example $75k → $69,262.50 base for SE tax.

SS Tax 12.4%: 12.4% on SS taxable up to wage base minus W-2 wages. Example $69,262.50×12.4% = $8,588.55 if no W-2.

Medicare 2.9% + 0.9%: 2.9% on all SE base plus 0.9% additional over $200k single/$250k joint. Example $69,262.50×2.9%=$2,008.61 no additional at $75k.

SE Tax 15.3%: SS + Medicare. Example $8,588.55+$2,008.61=$10,597.16.

Half Deductible: Half SE tax deductible for income tax. Example $5,298.58 reduces federal taxable.

Federal Est: Federal income tax on net minus half deduction minus standard deduction minus retirement using progressive brackets. Example $54,701 taxable → $6,948 federal.

Total Tax: SE + Federal + State. Shows true cost of self employment vs W-2.

Example — Varied Comparisons

Base: $75k net single $0 W-2 CA → SE Base $69,263 SE Tax $10,597 Half $5,299 Fed taxable $54,701 Fed $6,948 Total ~$20,045.

With $100k W-2 wages: Net $75k SE Base $69,263 SS taxable = Min($69,263, $176,100-$100k=$76,100) = $69,263 still same, SS $8,588. If W-2 $150k, SS taxable = $26,100 ×12.4%=$3,236.40 SS drops $5,352.

Texas no tax vs California: Same $75k Texas state $0 total ~$17,545 vs California state ~$2,500 total ~$20,045 difference $2,500 due to state.

$150k net vs $75k net: $150k net SE Base $138,525 SS taxable $138,525×12.4%=$17,177 Medicare $4,017 + additional 0% since under $200k threshold? Actually $150k SE base over $200k? No $138,525 under $200k, so no additional. SE Tax $21,194 Half $10,597 Fed taxable $150k-$10,597-$15k=$124,403 Fed ~$22k total ~$43k vs $75k total ~$20k.

Joint filing vs Single $75k: Single std $15k taxable $54,701 fed $6,948 vs Joint std $30k taxable $39,701 fed $4,394 difference $2,554 less federal joint.

Common Mistakes

1. Forgetting 92.35%: Using 100% of net for 15.3% overstates SE tax by 7.65%. Example $75k×15.3%=$11,475 vs correct $69,263×15.3%=$10,597 difference $878.
2. Ignoring wage base with W-2: If you have $150k W-2, only $26,100 of SE base gets 12.4% SS. Using full $69k overstates SS by $5k.
3. Mixing half deduction with full: Only half SE tax is deductible, not full. Example SE $10,597 half $5,299 deductible, not $10,597.
4. Thinking SE tax is income tax: SE tax is FICA for self employed separate from federal income tax. You pay both. Example $75k SE $10,597 + federal $6,948 = $17,545 before state.
5. Forgetting additional Medicare: Over $200k single additional 0.9% Medicare applies on top of 2.9%. Example $250k SE base $230,875 Medicare $230,875×2.9%=$6,695 + $30,875×0.9%=$278 additional total $6,973 Medicare not $6,695.

Practical Tip

Contribute to SEP IRA or Solo 401k to reduce income tax — retirement percent reduces federal taxable and state taxable but not SE tax base. Example $75k net 10% SEP $7,500 reduces federal taxable from $54,701 to $47,201 federal drops about $900 at 12% marginal. Track quarterly 1040-ES — SE tax plus federal plus state divided by 4 is your quarterly estimate to avoid penalty. Keep W-2 wages in mind for SS base to avoid double counting.

Important Limitations

This tool provides estimates for educational purposes only. Not tax, financial, or legal advice. Results depend on inputs you provide. SE tax rules, wage base $176,100, brackets, standard deduction, retirement limits and state rules change. Does not include credits, AMT, NIIT beyond additional Medicare, qualified business income deduction 199A, local taxes, or business structure specifics S-Corp vs sole proprietor. Does not model self employment loss, carryover, or alternative minimum. Verify with IRS Schedule SE, Publication 334, IRS.gov and qualified tax professional. Inputs are processed in your browser and not sent to a server for this calculator component.

Frequently Asked Questions

How is self employment tax calculated?

Self employment tax is 15.3% on 92.35% of net business income. 12.4% Social Security on base up to wage base $176,100 and 2.9% Medicare on all base plus 0.9% additional Medicare over $200k single or $250k joint. Half of SE tax is deductible for income tax.

Why 92.35% of income?

IRS allows 92.35% because employer half of FICA would be excluded if you were employee. Net $75k times 92.35% = $69,262.50 base for SE tax, SE tax = $69,262.50 times 15.3% = $10,597.16.

What is half deduction?

Half of SE tax is deductible for federal income tax. Example SE tax $10,597 half $5,298 reduces federal taxable income, saving federal tax at marginal rate.

Do I pay both federal and SE tax?

Yes. SE tax is FICA for self employed 15.3%. Federal income tax is separate using brackets after standard deduction and half SE deduction. Total tax = SE tax plus federal plus state.

What about Social Security wage base?

Social Security 12.4% applies only up to wage base $176,100 combined W-2 wages and SE base. If you have $100k W-2 wages, only $76,100 of SE base is subject to 12.4%, rest only Medicare.

Is there additional Medicare?

Yes. Additional 0.9% Medicare on SE base over $200k single, $250k joint, $125k married separate. This is on top of 2.9% Medicare.

Does this calculator save data?

No. Calculation runs in your browser. Inputs are not sent to a server for this calculator component. Closing tab clears values.