How to Calculate 401(k) Catch-Up Contributions

What a 401(k) catch-up is

Workers 50 and older may defer more than the 2026 base limit of $24,500.00: $8,000.00 extra from age 50, and $11,250.00 extra at ages 60–63 — the “super catch-up,” which replaces the $8,000.00. At 64 you drop back to the $8,000.00 catch-up. The age band is by your age on December 31, 2026. From 2026, prior-year FICA wages over $150,000.00 from the same employer force the catch-up to be Roth. Every figure here is checked against the 401(k) catch-up calculator.

The 401(k) catch-up formula

In one line: max deferral = $24,500.00 + catch-up for your age band; room left = max − what you already defer; tax saved = catch-up × marginal rate; future value = catch-up × ((1 + return)^years − 1) ÷ return. The catch-up is $0 under 50, $8,000.00 at 50–59 or 64+, and $11,250.00 at 60–63, with contributions at the end of each year.

Step 1: Find your age band on December 31, 2026

Find your age band on December 31, 2026, first — the band sets everything downstream. There are three bands: under 50, where the catch-up is $0; 50–59 or 64 and older, where it is $8,000.00; and 60–63, where it is the $11,250.00 super catch-up. The example here is a 61-year-old, so the band is 60–63. The band is by your age on the last day of the year — turn 60 in December and the super catch-up applies to the whole year.

Step 2: Take the 2026 base limit and add the catch-up for your band

Take the 2026 base limit of $24,500.00 and add the catch-up for your band to get your max. At 61 that is $24,500.00 + $11,250.00, or $35,750.00. Under 50 the max is the base alone, $24,500.00; at 50–59 or 64+ it is $24,500.00 + $8,000.00, or $32,500.00. The super catch-up replaces the regular catch-up — it does not stack — so no max is $24,500.00 + $8,000.00 + $11,250.00. The max is the ceiling on your deferral, divided by 12 in Step 6.

Step 3: Subtract what you already defer

Subtract what you already defer from your max to get the room left. The example defers $24,500.00, the 2026 base limit, so the room left at 61 is $35,750.00 − $24,500.00, or $11,250.00 — exactly the catch-up itself. If you defer nothing, the room is the whole max, $35,750.00. If you already defer the max, the room is $0.00. Room left is floored at $0.00.

Step 4: Multiply the catch-up by your marginal rate

Multiply the catch-up by your marginal rate for the tax saved. At 22% the tax saved is $11,250.00 × 22%, or $2,475.00 a year; at 12% it is $1,350.00 a year. The tax rate never changes the max or the future value — it only changes the tax saved — and it only applies to pre-tax deferrals: a Roth catch-up saves $0 now. Prior-year FICA wages over $150,000.00 from the same employer force the catch-up to be Roth.

Step 5: Project the catch-up forward

Project the catch-up forward with the annuity factor, ((1 + return)^years − 1) ÷ return. At 7% over 6 years the factor is 7.1532907, so $11,250.00 a year grows to $80,474.52. The factor exceeds 6 because early contributions compound for years. At 5% over 6 years the future value is only $76,521.52, and over 15 years at 7% it is $282,701.50 — nine more years more than triples the value.

Step 6: Divide your max by 12 and check the Roth mandate and the cap

Divide your max by 12 for the monthly payroll amount, and check the Roth mandate and the $72,000.00 cap. At 61 the monthly amount is $35,750.00 ÷ 12, or $2,979.17. The Roth mandate asks whether your prior-year FICA wages from the same employer exceeded $150,000.00: on $120,000.00 the answer is No; on $160,000.00 it is Yes, the catch-up must be Roth, and the tax saved disappears. The match is $120,000.00 × 3%, or $3,600.00, so total additions are $39,350.00 — under the cap.

Worked example

Put the six steps together for a 61-year-old on $120,000.00 who defers $24,500.00, with a 3% match, a 7% return, 6 years to retirement, and a 22% marginal rate. Catch-up $11,250.00; max $35,750.00; room $11,250.00; tax saved $2,475.00 a year; future value $80,474.52; match $3,600.00; total $39,350.00; monthly $2,979.17; Roth mandate No. Totals use unrounded values, so rounded parts may differ by a cent.

How time and return change the answer

Time matters more than most people expect. Stretch the same $11,250.00 catch-up to 15 years at 7% and the future value rises to $282,701.50, more than triple the 6-year $80,474.52. The return matters just as much the other way: at 5% over 6 years the future value is only $76,521.52, $3,953.00 less than at 7%. And the age boundary matters most of all: at 59 the catch-up is $8,000.00, worth $57,226.33 over 6 years at 7%; at 60 it is $11,250.00, worth $80,474.52.

Working backwards

It also runs in reverse: to leave exactly $5,000.00 of room at 61, defer $30,750.00. To save exactly $3,000.00 a year in tax, the marginal rate must be 26.67% (exact 26.6667%), giving $3,000.38; 26.66% gives $2,999.25 and 26.68% gives $3,001.50. To reach $100,000.00, the catch-up needs 8 years at 7%: $115,422.78 at 8 years, $97,357.74 at 7. To reach $150,000.00 in 10 years, the return must be 6.24% (exact 6.2448%), giving $149,965.89. To reach $100,000.00 in 6 years, it must be 15.61% (exact 15.6070%), giving $100,007.50.

What the calculation leaves out

Five things are left out. First, plan fees, which reduce the return the account actually earns. Second, the employer match formula: the match here is salary times the match percent, but many plans match only up to a percent of pay, or vest over time. Third, the $150,000.00 Roth threshold is tested against prior-year FICA wages from the same employer, not the salary you type in. Fourth, the $360,000.00 compensation cap and the $72,000.00 total-additions cap are not binding limits here. Fifth, state taxes, required minimum distributions, and leaving the employer. For the 2026 limits themselves, see the 2026 retirement contribution limits page.

What to do next

Run your own numbers through the 401(k) catch-up calculator — and if you are 59, check what turning 60 does to your max before the year ends.