401(k) optimizer

calculator

Am I leaving employer money on the table?

Runs your plan year pay period by pay period against the current IRS limits, prices the match you are declining, and settles traditional versus Roth in one comparison of two tax rates.

Your plan

Annual salary

You contribute6.0%

$138 per paycheck.

Your age

Paid

Employer match

Your summary plan description states this in one line.

My plan trues up the match at year end

Without a true-up the match is calculated each paycheck and never revisited.

Traditional or Roth

Your marginal tax rate now22%

Rate you expect in retirement22%

The match

The only part of this that is a guaranteed, immediate return.

Employer money you collect: $2,400
Left unclaimed: $0
Return on your next dollar: —

100% of the $2,400 this formula can pay at your salary.

Traditional or Roth

One comparison of two tax rates. Everything else cancels.

At equal rates it is a genuine tie

You expect to pay 22% in retirement against 22% today. When the two rates match, the two accounts produce identical after-tax money — the choice becomes about flexibility and about hedging future rate changes, not about arithmetic.

Traditional
$26,186
Roth
$26,186

After-tax money in 33 years, for the same $2,808 out of this year's take-home pay.

Compared on equal cost to you today, the ratio between the two is exactly (1 − 22%) ÷ (1 − 22%). Your return, your horizon and the size of the contribution all cancel out. Anyone selling you Roth on the strength of “tax-free growth” is quoting half of that fraction.

2026 limits

What the statute lets into the account, and how much of it you are using.

Your deferral limit: $24,500
You are contributing: $3,600
Room left this year: $20,900

Your $3,600 plus $2,400 of employer money is $6,000 of the $72,000 the plan may receive on your behalf.

Source

Figures are the 2026 statutory limits published by the IRS, 401(k) and profit-sharing plan contribution limits. They are adjusted for inflation each autumn for the year ahead.

Why this matters

An employer match is the only return in personal finance that is both large and certain. A 50% match is an immediate 50% on the money — before any market return, in a year when the market may well fall. Nothing else on this site comes close, which is why the match sits above paying off expensive debt in the plan ordering.

The two ways people lose it are quiet. The first is contributing below the full-match rate, which is visible if you look. The second is contributing so much that the annual deferral limit stops your paychecks in the autumn — in a plan that calculates the match per paycheck and never trues it up, the match stops too. Both are settled by the contribution percentage box in a payroll portal, which is the least examined field in American personal finance.

The traditional-versus-Roth question is smaller than it is made to sound. On equal cost to your take-home pay, the whole decision is whether your marginal rate in retirement will be below today's. Growth cancels. The one asymmetry worth knowing is at the ceiling: the limit caps the gross contribution, so someone maxing out shelters more real money in a Roth — at a correspondingly higher cost today.