401(k) Employer Match Optimizer Calculator

401(k) Employer Match

Most employer matches follow a simple percentage formula:

• “100% of the first 3% you contribute”: you put in 3%, employer adds 3% (3% of salary)
• “50% of up to 6%”: you put in 6%, employer adds 3% (50% of 6%)
• “100% of first 4% + 50% of next 2%”: tiered, max match 5%

Common formulas:

The “free money” rule: Always contribute at least enough to capture the full match. Employer match is part of total compensation. Leaving it on the table is equivalent to refusing a raise.

The IRS caps how much you can defer, and for higher earners the cap binds before your contribution percentage does. Someone on $400,000 electing 15% would be putting in $60,000, which is more than double what the law allows. The calculator below enforces the limit and tells you the percentage that actually gets you to it.

The employee deferral limit was $23,500 in 2025 ($31,000 with the age-50 catch-up), against a combined employee-plus-employer-plus-after-tax ceiling of $70,000. The figures are indexed and move most years, which is why the limit is an editable field below rather than a number baked into the math. Check the current one on the IRS website before relying on it.

There is a second cap people miss: only the first ~$350,000 of pay counts as compensation for plan purposes, so on a very large salary the match stops growing even though the salary does not.

Match formula math examples:

Example 1: Salary $80,000, formula 50% of 6%, contribute 6%

• Your contribution: $80,000 × 6% = $4,800
• Match: $4,800 × 50% = $2,400 (or 3% of salary)
• Total: $7,200

Example 2: Same salary, contribute 4% (under match cap)

• Your: $3,200
• Match: $3,200 × 50% = $1,600
• Total: $4,800
• You missed $800/year of free money ($2,400 - $1,600)

Example 3: Salary $80,000, contribute 15% (over match cap)

• Your: $12,000
• Match: still capped at $2,400 (50% of 6%)
• Total: $14,400: extra contribution is your money, not matched

True-up provisions: Some plans match per-paycheck (you must spread contribution across the year), others have a year-end “true-up” (back-fill match if you front-loaded contributions).

Without true-up: if you max out by July, you stop getting matches Aug-Dec, losing 5+ months of match. With true-up: front-loading is safe, the company catches up at year-end.

Always check your plan documents for true-up clauses. Without a true-up, contribute steadily through the year, not lump-sum.

Vesting schedules:

If you leave before fully vested, you forfeit the unvested portion of match. Bonus consideration when accepting a new job.

Mega backdoor Roth (advanced): If your plan allows after-tax contributions and in-service withdrawals, you can get up to $70,000 total into a 401(k), then convert the after-tax portion to a Roth. Few plans offer it, so check your Summary Plan Description before counting on it.