1099 Tax Estimator

The calculator has four inputs, plus a fifth for married couples. Work through them in order; the results on the right update as you type. If you've saved your numbers on the dashboard, your W-2 income, your spouse's income, 1099 revenue and filing status start from those, and you can change any of them.

1. Your W-2 Wages. Your expected taxable wages from your main job for the year. Box 1 of last year's W-2 is a good starting point if your pay hasn't changed. Otherwise, take the year-to-date taxable wages on your latest pay stub and project them to 12 months. Pre-tax 403(b) or 401(k) deferrals and health premiums come out of taxable wages, so the number is usually lower than your contract salary. The calculator also uses this figure to decide how much of the Social Security wage base your job has already used. The default is $280,000.
2. Gross Revenue (1099 side gig). Everything you expect to be paid this year as an independent contractor: locums, moonlighting shifts, consulting, expert witness or chart review work. If the work continues from last year, add up last year's 1099-NEC forms. If it's new, multiply your expected shifts by the shift rate. If a moonlighting job pays you on a W-2 instead, add that pay to the W-2 field. The default is $45,000.
3. Expenses. Deductible costs of that 1099 work, such as licenses and DEA registration for the side job, malpractice coverage you pay yourself, travel to assignments, and professional fees. If you filed a Schedule C last year, its total expenses line is a reasonable guide. The calculator subtracts expenses from revenue and shows the result as Net Profit under the fields; it never lets profit go below zero. The default is $2,000.
4. Filing Status. Choose Single or Married Joint to match the return you'll file, usually the same status as last year's Form 1040. Head of household and married filing separately aren't offered. If you're married and your spouse works, see the next input.
5. Spouse's W-2 Wages (Married Joint only). Your spouse's expected taxable wages for the year, from the same sources as yours; enter 0 if they have none. They count toward your joint income tax and the $250,000 joint threshold for the Additional Medicare Tax, but not toward your Social Security wage base, which applies to each person separately. The default is $0.

The results show three numbers. Estimated Quarterly Payment is the annual tax on your 1099 profit divided by four. Total Tax for Year (1099 Only) is the federal income tax, self-employment tax and Additional Medicare Tax that the side work adds. Effective Tax Rate is that total divided by your net profit, so you can see how many cents of each 1099 dollar to set aside.

Your hospital or group withholds federal income tax, Social Security and Medicare from every W-2 paycheck. A locums agency, a moonlighting site that pays on a 1099, or a consulting client withholds nothing. You owe income tax and self-employment tax on that money yourself, usually in four estimated payments during the year. Locums physicians run into this most often; our locum tenens salary guide walks through what that looks like for a full year of 1099 work.

Waiting until April can cost you. You generally have to make estimated payments if you expect to owe at least $1,000 after withholding, and you avoid an underpayment penalty only if you paid at least 90% of this year's tax or 100% of last year's (110% if last year's adjusted gross income was over $150,000) on time. Most attendings are in the 110% group. The 1099 physician taxes guide covers the due dates and safe harbors in detail.

Two-earner households have a second problem. Each employer withholds as if its paycheck were your only income unless you check Step 2 on your Form W-4, so two physician salaries together can be under-withheld before any 1099 income is added. This calculator assumes your W-2 withholding is already right and estimates only the extra tax the side work creates. If it isn't, fix the W-4 first.

The calculator works in six steps, all for tax year 2026, and treats your 1099 profit as income stacked on top of your W-2 wages.

1. Net profit: max(0, 1099 revenue − expenses).

2. Self-employment earnings: net profit × 92.35%. 92.35% is 100% minus 7.65%, the employer's share of payroll tax; Schedule SE makes this adjustment so self-employed people are taxed on the same base as employees.

3. Self-employment tax: 12.4% Social Security on the smaller of your self-employment earnings or max(0, $184,500 − W-2 income), plus 2.9% Medicare on all of your self-employment earnings. If your W-2 income is $184,500 or more, the Social Security part is zero.

4. Additional Medicare Tax: 0.9% × [max(0, wages + SE earnings − threshold) − max(0, wages − threshold)], where wages are your W-2 wages plus, if married filing jointly, your spouse's, with a threshold of $200,000 single or $250,000 married filing jointly. Only the part of the tax the 1099 work adds is counted.

5. Federal income tax on the 1099 profit: the tax on wages + net profit − half of SE tax − standard deduction minus the tax on wages − standard deduction, both from the 2026 brackets for your filing status, where wages include a spouse's W-2 wages on a joint return. The standard deduction is $16,100 single or $32,200 married filing jointly, the amounts the One Big Beautiful Bill Act made permanent and the IRS adjusted for 2026. Because the W-2 is taxed first, the profit lands in your top bracket.

6. Results: total = step 5 + step 3 + step 4. The quarterly payment is the total divided by 4, and the effective rate is the total divided by net profit.

Nothing else enters the calculation: no state tax, no qualified business income (QBI) deduction, no credits. The Assumptions & Sources section below lists everything left out.

• Pearl: you can fix it through your paycheck. Federal withholding is treated as paid evenly through the year (Form 2210 instructions), so a physician who picks up 1099 work midyear can raise withholding at the day job instead of mailing estimates. Divide the calculator's total by your remaining paychecks and enter it in Step 4(c) of a new Form W-4.
• Pearl: enter a working spouse's wages in their own field. Lumping both salaries into your W-2 field would use up your Social Security wage base with your spouse's pay and understate your self-employment tax, because the wage base applies to each person separately. The separate field keeps the brackets and the Additional Medicare threshold right without that error.
• Pitfall: residents pay the full 15.3%. A resident's salary is far below the wage base, so 1099 moonlighting owes Social Security and Medicare on 92.35% of profit. In the worked example above, that pushes the resident's share to 34.6% of profit, compared with 27.2% for the married attending.
• Pitfall: state tax isn't included. The result is federal only. If your state taxes income, add your state's rate on the 1099 profit, and check whether it also expects quarterly estimates.
• Pearl: a solo 401(k) lowers the income tax part. Your side business can contribute up to 20% of net self-employment earnings, figured after the deduction for half of self-employment tax (IRS Publication 560). The $24,500 employee deferral limit for 2026 is shared with your day job's 401(k) or 403(b), so if you max that plan, only the employer contribution is left. The contribution does not reduce self-employment tax.
• Pitfall: lumpy income. The calculator splits the year into four equal payments. If most of your 1099 income arrives late in the year, the annualized installment method on Form 2210 may let you pay less in the early quarters.