● Money & small business
How much will an HSA or 401(k) contribution reduce my paycheck? Tables for 2027
When you raise a pre-tax deduction at open enrollment, your paycheck doesn't fall by the whole amount: the money isn't taxed, so part of it comes out of the tax you would have paid. How much depends on how the deduction is taken and on your tax rates. Every figure below comes from our open enrollment paycheck calculator, which was checked against its spreadsheet and an independent calculation for 401 benefit lists. We assume 26 paychecks and a 5% state income tax; use your own numbers in the calculator.
Three ways a deduction can be taken
- Pre-tax through a cafeteria plan: health, dental and vision premiums, HSA contributions through payroll, health and dependent care FSAs. These skip federal and state income tax and FICA (Social Security and Medicare, 7.65% on pay up to the $184,500 wage base in 2026).
- Pre-tax 401(k) or 403(b): skips income tax, but FICA is still taken.
- Roth or after-tax: taxed as usual now, so the full amount comes out of your take-home pay.
Maxing out an HSA in 2027
The 2027 HSA limit is $4,500 for self-only coverage and $9,000 for family coverage (IRS Rev. Proc. 2026-24), including any employer money. With no employer contribution, that's $173.07 or $346.15 a paycheck (per-paycheck table for other pay schedules). What it does to take-home pay:
| Federal bracket | Family: take-home down | Tax saved a year | Self-only: take-home down | Tax saved a year |
|---|---|---|---|---|
| 10% | $267.75 | $2,038.48 | $133.87 | $1,019.21 |
| 12% | $260.82 | $2,218.48 | $130.41 | $1,109.21 |
| 22% | $226.21 | $3,118.47 | $113.10 | $1,559.19 |
| 24% | $219.29 | $3,298.46 | $109.64 | $1,649.18 |
| 32% | $191.59 | $4,018.46 | $95.79 | $2,009.17 |
So in the 22% bracket, putting $8,999.90 in a family HSA ($346.15 a paycheck) lowers your take-home pay by $226.21 a paycheck, $5,881.43 over the year; the other $3,118.47 is tax you no longer pay. Your state matters too: in the 24% bracket, the family HSA lowers take-home pay by $236.59 with no state income tax and by $204.40 at a 9.3% state rate. If you earn above the Social Security wage base, only the 1.45% Medicare part of FICA is saved: $240.75 a paycheck in the 24% bracket. A few states, such as California and New Jersey, tax HSA contributions; for those, enter 0 as the state rate in the calculator.
$500 a paycheck: pre-tax 401(k), Roth, or cafeteria plan
| Federal bracket | Pre-tax 401(k): take-home down | Roth 401(k): take-home down | Cafeteria plan (e.g. premiums): take-home down |
|---|---|---|---|
| 12% | $415.00 | $500.00 | $376.75 |
| 22% | $365.00 | $500.00 | $326.75 |
| 24% | $355.00 | $500.00 | $316.75 |
| 32% | $315.00 | $500.00 | $276.75 |
A pre-tax 401(k) saves your federal bracket plus the state rate on every dollar: in the 22% bracket, $3,510 a year on $13,000 of contributions. The Roth version saves nothing now but its withdrawals in retirement are tax-free, which is a different trade-off: Roth or traditional by tax rate works through it. Moving $500 a paycheck from pre-tax to Roth lowers take-home pay by $135 in the 22% bracket.
Several changes at once
Open enrollment usually changes several things together. In the calculator's example, a family moves from a PPO to a high-deductible plan with an HSA, raises the dependent care FSA and adds a Roth 401(k): $1,027.77 comes out of each paycheck instead of $688.45, $339.32 more, but take-home pay falls by only $239.55, because the tax saved rises from $5,789.15 to $8,383.25 a year. Try your own elections; the spreadsheet version adds up to 25 benefits, employer money and checks against the 2027 limits.
These are estimates at fixed tax rates: a large change can move part of your income into another bracket, and your employer's payroll system rounds its own way. Not tax advice.