Retirement · Employer match · Monthly

401(k) Compound Interest

Project a realistic retirement balance with employer-matched monthly contributions, decades of monthly compounding, and inflation adjusted to today's dollars.

Load scenario25 → 65, 7% match 35 → 65, catch-up Max contribution

Live·Updates on every change

Inputs

Currency

Initial amount

Annual interest rate

Time horizon

Years:

Months:

Compound frequency

Regular contributions: (optional)

Deposit amount: (optional)

Annual deposit increase? (optional)

Inflation & tax⌄

Annual inflation rate

Shown as a "real" value in today's money.

Tax on gains

Applied once at the end of the horizon.

Future value

—

After

—

Contributed

—

Principal + deposits

Interest earned

—

Effective APY

—

Growth over time

Principal, contributions, and interest — stacked year by year.

PrincipalContributionsInterest

Year-by-year breakdown

Opening balance, deposits, interest, closing balance.

Show table

Year	Opening	Net flows	Interest	Closing

Why this preset

A 401(k) is monthly deposits + decades.

Nearly every 401(k) is funded by payroll — monthly or bi-weekly — and nearly every plan compounds monthly behind the scenes. This 401k compound interest calculator is pre-wired for exactly that: monthly compounding, monthly deposits, end-of-period timing, inflation on. Add your own contribution and the employer match together into one monthly amount and you'll see the real number the day you retire.

Example · 40 years, 8%, $1,200/mo

Contributed (you + match)$576,000
Interest earned~$3.19M
Future value (nominal)~$3.77M
In today's dollars (3% infl.)~$1.15M

FAQ

Frequently asked

How do I include the employer match?

Add your contribution and your employer's match together and enter the total as the Deposit amount. For example, if you put in $500 a month and your employer matches it dollar for dollar, enter $1,000.

What rate should I use for a 401(k)?

The long-run US stock market averages 7–10% nominal before fees. A conservative projection uses 7%; an aggressive one uses 9%. Subtract 0.5–1% for fund expense ratios in actively managed funds.

Should I turn on tax on gains?

No — a traditional 401(k) is tax-deferred and withdrawals are taxed as ordinary income later, so during the growth phase keep the tax field at 0. Model the eventual tax drag separately when planning distributions.

What are the 2026 401(k) contribution limits?

For 2026 you can contribute up to $24,500 (about $2,042 a month). If you're 50 or older you can add an $8,000 catch-up, or $11,250 if you're 60–63. Employer matching contributions don't count toward your $24,500. The limits rise most years, so check irs.gov before you plan.

Does it work for a Roth 401(k)?

Yes — the compounding math is identical. The difference is tax treatment at withdrawal, not during growth. Use the same calculator and leave the tax field at 0.

Your 401(k) in one chart.

Move the rate, horizon, or monthly deposit — the retirement number updates live.

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