Social Security tax is calculated with one multiplication: take your Social Security wages for the pay period and multiply by 6.2%. If you earn $2,000 in a biweekly paycheck and have no pre-tax health deductions, that is $2,000 x 6.2% = $124.00 taken out for Social Security. Your employer pays another $124.00 on top of it, so $248.00 goes in under your name.
There are only two wrinkles. The 6.2% stops once your year-to-date Social Security wages pass $184,500 in 2026, and not every deduction lowers the wage amount the tax is figured on. A $52,000 salary loses $3,224 a year to this tax; a $210,000 salary loses $11,439 and then stops. Here is how payroll actually runs the numbers on your check.
Your employer does not guess. Each pay period, payroll takes your gross pay, subtracts any deductions that are exempt from Social Security tax (most commonly health insurance premiums and HSA or FSA contributions run through the employer's plan), and calls the result your Social Security wages. That figure is multiplied by 6.2%. There is no standard deduction, no bracket, and no W-4 setting that changes it. The $16,100 standard deduction that shelters part of your pay from federal income tax in 2026 does nothing here.
Say your gross biweekly pay is $3,200 and you pay $180 for health insurance on a pre-tax basis. Your Social Security wages are $3,020, not $3,200. The tax is $3,020 x 6.2% = $187.24. If you also put $250 into a traditional 401(k), that $250 does not come off the top for Social Security purposes. A 401(k) lowers your income-tax wages; it leaves your Social Security wages alone. That mix-up is the most common reason a hand calculation comes out a few dollars lower than the pay stub.
The employer then matches your 6.2% with another 6.2% of its own money. You never see that half on your stub, but it is part of the same calculation. Between the two of you, 12.4% of your Social Security wages is sent in each pay period, up to the yearly cap. When people talk about the combined payroll cost of hiring, this matched half is a big piece of it.
Medicare is figured right next to it but it is a separate tax: 1.45% on all wages with no cap, plus an extra 0.9% on wages over $200,000. Do not fold those numbers into the Social Security line. On your stub they may sit side by side, sometimes under older labels like OASDI for Social Security and HI for Medicare, but the math behind each one is different.
A $52,000 salary, paid biweekly. Gross pay per check is $2,000. With no pre-tax health deductions, Social Security tax is $2,000 x 6.2% = $124.00 per check. Over 26 paychecks that is $3,224 for the year, and your employer adds another $3,224. Simple, because $52,000 sits well under the $184,500 wage base, so the 6.2% runs all year without interruption.
A $95,000 salary with health insurance. Gross biweekly pay is $3,653.85. You pay $220 per check for health premiums pre-tax, so Social Security wages are $3,433.85. The tax is $3,433.85 x 6.2% = $212.90 per check, about $5,535 a year. Had you figured 6.2% on the full $3,653.85, you would have gotten $226.54 and wondered why the stub disagreed with you. The $220 premium explains the whole gap.
A $210,000 salary and the cap. Gross biweekly pay is $8,076.92. For most of the year the tax is $8,076.92 x 6.2% = $500.77 per check. But your year-to-date wages reach $184,500 partway through the year, after roughly 23 paychecks. On that paycheck only the slice of pay that fits under $184,500 is taxed; from the next check on, the Social Security line is $0. Your total for 2026 is not $210,000 x 6.2% ($13,020). It is $184,500 x 6.2% = $11,439, the most any employee pays into Social Security this year.
Bonuses, commissions, and overtime all feed into the same running total. A $10,000 bonus paid in March is Social Security wages in March. If you are under the cap, $620 comes out of it for Social Security, on top of the 22% federal withholding and 1.45% Medicare. If the bonus lands after you have already crossed $184,500, no Social Security tax comes out at all, which is one reason a late-year bonus can look oddly generous next to an early-year one.
The $184,500 limit is tracked per calendar year and, here is the part that catches people, per employer. Your payroll system only knows what it has paid you. Start a new job in July after earning $150,000 at the old one, and the new employer starts your count at zero. By December you may have paid Social Security tax on well over $184,500 of combined wages.
That overpayment is not lost. When you file your tax return, the excess employee Social Security tax is claimed as a credit and comes back to you. Your two employers, however, do not get their matching halves back, and neither employer did anything wrong. Each one followed the rule correctly with the wages it could see. If you hold two jobs at the same time, the same thing can happen on a smaller scale all year long.
The opposite situation shows up in a single high-paying job. Once you cross the cap, take-home pay jumps because 6.2% of every check suddenly stays in your pocket. On an $8,076.92 biweekly check, that is about $500 more per check for the rest of the year. People sometimes call payroll convinced something broke. Nothing broke. The wage base was reached, and on January 1 the counter resets and the tax starts again from the first dollar.
The tax is figured on wages for work: salary, hourly pay, overtime, tips your employer knows about, commissions, bonuses, and paid time off you take. Severance pay counts too. If it shows up as pay for your job, it almost always counts toward both the 6.2% calculation and the $184,500 running total.
What gets subtracted before the multiplication is short: pre-tax health, dental, and vision premiums, and money you run through an employer-sponsored HSA or health FSA. Those dollars are out of your Social Security wages, your Medicare wages, and your income-tax wages all at once. Group-term life insurance over $50,000 of coverage works the other way and can add a small amount of taxable wages you never see in cash.
Retirement contributions are where the confusion lives. Money you defer into a 401(k) or 403(b) escapes federal income tax today, which is why your W-2 Box 1 (income-tax wages) is often lower than your Box 3 (Social Security wages). The deferral does not escape Social Security tax. If Box 1 says $78,000 and Box 3 says $88,000 on $90,000 of gross pay, the usual story is $10,000 of 401(k) deferrals plus $2,000 of pre-tax health premiums. Box 3 stopped at $88,000 because only the premiums came out. That gap is normal, and it is the fastest way to check whether payroll treated your deductions right.
Work for yourself and there is no employer to split the bill. You pay 12.4% for Social Security (the 6.2% employee half plus the 6.2% employer half) as part of the self-employment tax, on top of 2.9% for Medicare. The $184,500 wage base still applies, and wages from a day job count toward it. Earn $60,000 in W-2 wages and $140,000 from a side business, and only $124,500 of the business income is exposed to the 12.4% portion.
One adjustment softens it slightly. Self-employment tax is figured on 92.35% of your net business profit, not the full amount. Net $80,000 and the tax base is $73,880. The Social Security piece is $73,880 x 12.4% = $9,161.12, and Medicare is $73,880 x 2.9% = $2,142.52. You then deduct half of the total self-employment tax on your income tax return. That deduction lowers your income tax, not the payroll tax itself, but it keeps the two systems roughly fair between employees and the self-employed.
To check your own year, start with your last pay stub. Year-to-date Social Security tax divided by 0.062 should roughly equal your year-to-date Social Security wages, and that wage figure should never pass $184,500 with one employer. In January, do the same check on your W-2: Box 4 (Social Security tax withheld) should equal Box 3 (Social Security wages) times 6.2%, capped at $11,439 for 2026. If those numbers do not line up within a dollar of rounding, ask payroll while the records are still easy to pull. The FICA tax calculator will run the combined Social Security and Medicare math for any salary, and the take-home pay calculator shows where this tax sits inside the full paycheck.
Take your Social Security wages for the pay period (gross pay minus pre-tax health premiums and employer-plan HSA/FSA contributions) and multiply by 6.2%. A $2,500 check with $150 of pre-tax health premiums is $2,350 x 6.2% = $145.70. Traditional 401(k) contributions do not reduce the wage figure for this tax.
The most an employee pays is $11,439, which is 6.2% of the $184,500 wage base. Once your year-to-date Social Security wages pass $184,500, the tax stops for the rest of the year. Your employer matches up to another $11,439 on its side.
Yes. Bonuses, commissions, overtime, and tips are all Social Security wages and get the same 6.2% treatment until your year-to-date total reaches $184,500. A $10,000 bonus paid before you hit the cap loses $620 to Social Security tax, plus 1.45% Medicare and federal withholding.
Almost always because your year-to-date wages crossed the $184,500 wage base. Payroll stops the 6.2% deduction once the cap is reached, so your take-home pay rises for the remaining checks. It restarts at 6.2% on your first paycheck of the new year.
Each employer applies the $184,500 cap to only the wages it paid you, so two jobs can easily push you over. The excess employee tax is not lost: you claim it as a credit on your tax return and it is refunded. The employers' matching shares are not refunded.