The formula, in one paragraph
FICA tax has three parts. First, Social Security: 6.2% of your wages, but only up to the 2026 wage base of $184,500, so the most you pay is $11,439.00. Second, Medicare: 1.45% of all your wages, with no cap. Third, the additional Medicare tax: 0.9% of wages above $200,000 for single filers and $250,000 for married filing jointly. Add the three together and you have the employee FICA. Your employer matches the Social Security and Medicare, but not the additional tax. Subtract the employee FICA from your wages and you have the take-home after FICA.
Step 1: Work out the Social Security tax
Multiply your wages by 6.2%, but stop at the $184,500 wage base. At the example wages of $80,000 the whole amount is under the wage base, so the Social Security tax is 6.2% of $80,000, which is $4,960.00. At $184,500 the tax is $11,439.00, and at $185,000 it is still $11,439.00: the extra $500 adds $0.
Step 2: Work out the Medicare tax
Multiply your wages by 1.45%. There is no wage base and no cap, so every dollar counts. At the example wages the Medicare tax is 1.45% of $80,000, which is $1,160.00. At $1,000,000 of wages the Medicare tax is $14,500.00.
Step 3: Work out the additional Medicare tax
Compare your wages with the threshold: $200,000 for single filers, $250,000 for married filing jointly. The tax is 0.9% of the part above the threshold, and nothing if you are below it. At the example wages of $80,000 the additional tax is $0.00. At $250,000 single the additional tax is $450.00. The threshold is not indexed for inflation.
Step 4: Add them up — and match the employer
Add the Social Security tax, the Medicare tax and the additional Medicare tax. At the example wages that is $4,960.00 plus $1,160.00 plus $0.00, which is $6,120.00. That is the employee FICA, and the effective rate is $6,120.00 divided by $80,000, which is 7.65%. Your employer pays the same $6,120.00, but not the additional tax. The combined FICA is $12,240.00. A self-employed worker pays both halves through SECA, so the combined $12,240.00 is their tax.
Step 5: Work out the take-home after FICA
Subtract the employee FICA from your wages. At the example wages that is $80,000 minus $6,120.00, which is $73,880.00. That is the take-home after FICA, before income tax and other deductions. FICA is separate from federal income tax, and this guide does not work out income tax.
The same arithmetic at other wages
The same steps scale to any wage. On $50,000 the employee total is $3,825.00 and the take-home is $46,175.00. On $250,000 single the employee total is $15,514.00 and the take-home is $234,486.00. On $300,000 married filing jointly the employee total is $16,239.00 and the take-home is $283,761.00.
Working backwards from a target
The calculation also runs backwards. The wage that pays exactly $10,000 of employee FICA is $130,718.95, because 7.65% of $130,718.95 is $9,999.9997, which displays as $10,000.00. The wage that pays exactly $15,000 of employee FICA is $228,127.66. And the wage that leaves exactly $100,000 of take-home after FICA is $108,283.70.
When the Social Security cap stops the tax
The wage base is what makes FICA different from income tax. At $184,500 of wages the Social Security tax is $11,439.00, and at $185,000 it is still $11,439.00: the extra $500 adds $0 of Social Security tax. At $1,000,000 the employee total is $33,139.00 and the effective rate falls to 3.31%.
What NOT to do
Do not confuse FICA with income tax: the take-home after FICA is $73,880.00 at the example wages, and the take-home after everything is less. Do not assume the employer pays the additional tax: at $250,000 single the employer pays $15,064.00 and the employee $15,514.00.
That box is the whole formula.
Worked example: the $80,000 wage
Step 2: 1.45% of $80,000 = $1,160.00.
Step 3: $80,000 is below $200,000, so $0.00.
Step 4: $4,960.00 + $1,160.00 + $0.00 = $6,120.00.
Step 5: $80,000 − $6,120.00 = $73,880.00.
Answer: $6,120.00 employee FICA, $6,120.00 employer FICA, $12,240.00 combined, $73,880.00 take-home, 7.65% effective rate.