Self-Employment Tax & Quarterly Estimated Tax Calculator

Estimate your 2025 self-employment (Social Security + Medicare) tax under Schedule SE, the Additional Medicare Tax, the deduction for one-half of SE tax, and the quarterly estimated payment needed to meet a Form 1040-ES safe harbor.

1 Self-Employment & Wage Income

Enter your net profit from Schedule C and any W-2 wages already subject to Social Security and Medicare withholding this year. If you have more than one Schedule C business, add the net profits together for a single total.

Filing status

Net profit from self-employment (Schedule C, all businesses combined) *

Net profit before any SE-tax deduction — Schedule C, line 31 (summed across businesses).

W-2 wages already subject to Social Security & Medicare this year

From Form W-2, box 3 (Social Security wages). Default is $0 if you have no W-2 job.

2 Prior-Year & Current-Year Figures for 1040-ES safe harbor

Optional, but needed to estimate your required quarterly payment. If you leave a field blank (0), the calculator will show what it can and explain what's missing.

Prior year (2024) total tax liability

Form 1040 (2024), line 22 (or line 24, total tax) from your 2024 return.

Prior year (2024) adjusted gross income (AGI)

Form 1040 (2024), line 11. Determines whether the 110% safe-harbor rate applies.

Estimated current-year (2025) total tax liability

Optional — your projected 2025 income tax plus the SE tax and Additional Medicare Tax computed below.

3 Self-Employment Tax Calculation Schedule SE, Part I

Step-by-step build-up of your Social Security and Medicare tax on self-employment income.

Source & assumptions

2025 figures used: net SE earnings = net profit × 92.35% (IRC §1402(a), Schedule SE Part I); 2025 Social Security wage base = $176,100 (SSA 2025 COLA announcement / Rev. Proc. 2024-40); Social Security portion = 12.4% of net SE earnings up to the wage base, reduced by W-2 Social Security wages already subject to tax; Medicare portion = 2.9% of all net SE earnings, uncapped. See the 2025 Instructions for Schedule SE (Form 1040). Verify current figures against the final published 2025 Schedule SE instructions before relying on this estimate.

4 Additional Medicare Tax Form 8959

A separate 0.9% tax on combined wages and self-employment income above your filing-status threshold. It is not part of SE tax itself, is not eligible for the 50% deduction below, but is part of your total tax liability.

Source & assumptions

Additional Medicare Tax thresholds (not inflation-adjusted, fixed since 2013 under IRC §3101(b)(2) and §1401(b)(2)): $250,000 Married Filing Jointly; $125,000 Married Filing Separately; $200,000 Single, Head of Household, and Qualifying Surviving Spouse. Rate is 0.9% on the combined total of Medicare wages plus net SE earnings (92.35% of net profit) above the threshold. See Form 8959 and its instructions.

5 Deduction for One-Half of SE Tax Schedule 1, Line 15

Half of your Schedule SE tax (line 3 above, not the Additional Medicare Tax) is deductible in arriving at adjusted gross income. This reduces your income tax — it does not reduce the SE tax itself.

Total SE tax (from Step 3)

Deduction for AGI (50% of SE tax)

6 Quarterly Estimated Tax — Safe Harbor Form 1040-ES

To avoid an underpayment penalty, your total 2025 withholding + estimated payments generally need to meet the lesser of two tests below.

Required annual payment (safe harbor)

Estimated quarterly payment (÷ 4)

Underpayment penalty risk (Form 2210): if your withholding and timely estimated payments fall short of whichever safe-harbor amount applies to you, the IRS can charge an underpayment penalty (computed on Form 2210, based on the shortfall for each quarter and the federal short-term interest rate) — this calculator does not compute that penalty; it only estimates the payment needed to avoid it.

Source & 2025 due dates

IRC §6654(d)(1): required annual payment is the lesser of 90% of the current-year tax or 100% of the prior-year tax (110% if prior-year AGI exceeded $150,000, or $75,000 if Married Filing Separately). See the 2025 Instructions for Form 1040-ES. 2025 quarterly due dates: Q1 — April 15, 2025; Q2 — June 16, 2025; Q3 — September 15, 2025; Q4 — January 15, 2026.

7 Summary

Total SE tax

Additional Medicare Tax

Deduction for AGI

Est. quarterly payment

Important — read before relying on this estimate

This tool provides a simplified, educational ESTIMATE ONLY. It is not tax advice, not a guarantee of any outcome, and does not constitute a completed Schedule SE, Form 8959, Form 1040-ES, or any other filing. It does not account for: state or local income tax; the Additional Medicare Tax withheld by an employer on wages (which can offset the amount due with a return); self-employed health insurance or retirement-plan deductions that reduce net SE income for some purposes; multiple/mixed sources of self-employment and wage income across different employers; church employee income or other special SE categories; the optional methods for figuring SE tax; or your Alternative Minimum Tax or other credits and taxes that affect total liability. The Social Security wage base, Additional Medicare Tax thresholds, and safe-harbor rules used here are based on the best information available at the time this tool was built and should be verified against the final, published 2025 Schedule SE and Form 1040-ES instructions. Always confirm results with a qualified preparer before making a payment or filing.