Retirement / 401(k) Calculator

Future value equals the starting balance times one plus the monthly return raised to the number of months, plus the monthly contribution times the quantity one plus the monthly return raised to the number of months minus one, divided by the monthly return.

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Retirement Balance Projection

Project the balance of a 401(k), 403(b), or other matched workplace plan at retirement. The calculator grows your current balance and every monthly contribution — yours plus the employer match — at an assumed annual return compounded monthly, then splits the final balance into what you put in, what your employer added, and what compounding earned. For a traditional or Roth IRA, which has no salary-deferral match, set the employer match to 0%.

FV = P₀(1 + r)ⁿ + PMT · [((1 + r)ⁿ − 1) / r]

How It Works

A matched workplace plan like a 401(k) or 403(b) grows from three sources: your contributions, your employer's match, and investment returns compounding on the whole balance. (A traditional or Roth IRA has no employer match — set the match to 0% to model one.) This calculator models all three month by month. Each month it grows the prior balance by one-twelfth of the annual return, then adds your contribution (a percent of salary) and the employer match. The employer match is the often-overlooked free money: a typical plan matches 50% or 100% of what you contribute, but only up to a limit such as 6% of your pay. So if you contribute 10% and the match is 50% up to 6%, the employer adds 50% of 6% of salary — they do not match the extra 4%. Over a long horizon the compounding term dominates: a dollar contributed at age 30 has decades to double and redouble, which is why starting early and capturing the full match matter so much. The final balance is the future value of your starting amount plus the future value of the stream of monthly contributions.

Example Problem

You are 35 with $10,000 in your 401(k), earn $60,000, contribute 10% of pay, and your employer matches 50% of contributions up to 6% of salary. Assuming a 7% annual return, what will you have at 65 (30 years)?

  1. Monthly employee contribution = $60,000 × 10% ÷ 12 = $500.
  2. Matched salary fraction = min(10%, 6%) = 6%; employer match = $60,000 × 50% × 6% ÷ 12 = $150/month.
  3. Total monthly contribution = $500 + $150 = $650; monthly return r = 7% ÷ 12 ≈ 0.005833 over n = 360 months.
  4. Grow the $10,000 starting balance: 10,000 × (1.005833)^360 ≈ $81,156.
  5. Grow the contribution stream: 650 × [((1.005833)^360 − 1) / 0.005833] ≈ $792,900.
  6. Add them: balance at retirement ≈ $874,000 — your $10,000 starting balance plus $180,000 of contributions plus about $54,000 of employer match plus roughly $630,000 of investment growth.

Investment return is an assumption, not a guarantee — markets vary year to year, and the long-run average is not the return in any single year. The model also assumes a constant salary and contribution rate; real raises and contribution increases would push the balance higher.

When to Use Each Variable

  • Project your retirement balance — when you want to estimate what your 401(k), 403(b), or other matched workplace plan could be worth at retirement and see how much of it comes from the employer match versus compounding (for an IRA, set the match to 0%).

Key Concepts

Three ideas drive the result. First, the employer match is close to free money — a 50% match adds 50 cents per dollar you contribute before the market does anything, which is why financial advisors say to contribute at least enough to capture the full match. (This calculator treats the match as fully vested; many plans apply a vesting schedule, so employer money can be forfeited if you leave before you are vested — check your plan.) Second, compounding is exponential, not linear: the investment-growth share of the final balance grows faster than the contribution share as the horizon lengthens, so an extra five years early in a career can outweigh much larger contributions late. Third, the difference between a nominal annual return and what you actually earn comes down to compounding frequency and fees; this model compounds monthly and ignores fees and taxes, so it estimates a pre-tax, pre-fee balance. Traditional 401(k) balances are taxed on withdrawal, while Roth balances are not, so the same projected number means different after-tax wealth depending on the account type.

Applications

  • Deciding how much to contribute to capture the full employer match
  • Comparing the long-run impact of a 6% versus a 10% contribution rate
  • Estimating whether you are on track for a retirement savings target
  • Showing a younger worker the cost of delaying contributions by a few years
  • Quantifying how much of a projected balance is employer match versus your own savings
  • Sanity-checking a financial advisor's or plan provider's projection

Common Mistakes

  • Contributing less than the match limit — this leaves free employer money on the table, the single most expensive retirement-savings mistake.
  • Assuming the employer matches every dollar you contribute. Most plans match only up to a cap (e.g., 6% of salary); contributions above the cap get no match.
  • Treating the assumed return as guaranteed. A 7% long-run average does not mean 7% every year, and sequence-of-returns risk matters near retirement.
  • Ignoring fees and taxes. This model is pre-fee and pre-tax; a traditional 401(k) is taxed on withdrawal, which reduces spendable wealth.
  • Forgetting that inflation erodes purchasing power — a balance that looks large in today's dollars buys less in 30 years.
  • Never increasing the contribution rate. Holding contributions flat for a whole career understates what most savers actually accumulate as their pay rises.

Frequently Asked Questions

How do you calculate retirement savings growth?

Grow the current balance and every contribution at the assumed return. For r > 0 the future value is FV = P₀(1 + r)ⁿ + PMT × [((1 + r)ⁿ − 1) / r], where P₀ is the starting balance, PMT is the total monthly contribution (yours plus the employer match), r is the monthly return (annual ÷ 12), and n is the number of months; at a 0% return this reduces to FV = P₀ + PMT × n. This calculator evaluates that month by month so it can also show the year-by-year balance.

What is the formula for 401(k) growth with an employer match?

The growth formula is the same future-value-of-an-annuity equation; the match just increases the monthly contribution. Monthly match = (salary ÷ 12) × match rate × min(your contribution %, match limit %). For example, a 50% match up to 6% of a $60,000 salary adds $60,000 × 0.50 × 0.06 ÷ 12 = $150 per month on top of your own contribution.

How does an employer 401(k) match work?

Your employer adds money based on what you contribute, up to a limit. A common formula is '50% of contributions up to 6% of pay,' meaning the employer adds 50 cents per dollar you contribute on the first 6% of your salary. If you contribute more than 6%, the extra is not matched. Contributing at least up to the limit captures the full match — one of the highest-return moves available, subject to your plan's vesting schedule (employer money may be forfeited if you leave before it vests).

How much should I contribute to my 401(k)?

At a minimum, contribute enough to get the full employer match — otherwise you are turning down free money. Many advisors suggest saving 10–15% of pay (including the match) for retirement. Use the calculator to see how raising your contribution rate changes the projected balance, but always at least hit the match limit first.

What rate of return should I assume for retirement?

There is no guaranteed number. Historically a diversified stock-heavy portfolio has averaged roughly 7% per year after inflation over long periods, but returns vary widely year to year and past performance does not guarantee future results. Many planners model a range — for example 5%, 7%, and 9% — to see how sensitive the projection is to the assumption.

Does this calculator account for taxes and fees?

No. It projects a pre-tax, pre-fee balance. A traditional 401(k) is taxed as ordinary income when you withdraw, while a Roth 401(k) or Roth IRA is funded with after-tax dollars and qualified withdrawals are tax-free. Investment fees also reduce returns over time. Treat the result as an upper-bound estimate of the account balance, not spendable after-tax wealth.

Reference:

Future-value-of-an-annuity formula: Investopedia, Future Value of an Annuity (https://www.investopedia.com/retirement/calculating-present-and-future-value-of-annuities/). Employer match mechanics: Investopedia, How 401(k) Matching Works (https://www.investopedia.com/articles/personal-finance/112315/how-401k-matching-works.asp). Contribution and account rules: U.S. Internal Revenue Service, 401(k) Plans (https://www.irs.gov/retirement-plans/401k-plans). Employer-contribution vesting: U.S. Securities and Exchange Commission (Investor.gov), Vesting (https://www.investor.gov/introduction-investing/investing-basics/glossary/vesting).

Retirement Savings Formula

The projected balance is the future value of your starting amount plus the future value of the monthly contribution stream (yours plus the employer match), compounded monthly.

FV = P₀(1 + r)n + PMT × [((1 + r)n − 1) / r]Balance at retirement
FV = P₀ + PMT × nZero-return limit (r = 0): no growth, balance is just the deposits
Employer match = (salary / 12) × match rate × min(contribution %, limit %)Monthly employer contribution

Where:

  • FV — projected account balance at retirement
  • P₀ — current account balance
  • PMT — total monthly contribution (your contribution plus the employer match)
  • r — monthly return (annual return ÷ 12, as a decimal)
  • n — number of months (years × 12)

The employer only matches contributions up to the plan limit, so the matched fraction of your salary is the smaller of your contribution rate and the match limit. Contributions above the limit still grow but earn no additional match — the reason to contribute at least up to the limit before anything else.

Worked Examples

Capturing the Full Match

How much does contributing 6% vs. 3% change a 30-year balance?

A 35-year-old earning $60,000 has $10,000 saved and a 50%-up-to-6% employer match, assuming a 7% return for 30 years. Contributing 6% captures the full match; 3% leaves half the match unclaimed.

  • At 6%: employee $300/mo + employer $150/mo = $450/mo total
  • At 3%: employee $150/mo + employer $75/mo = $225/mo total
  • 6% balance ≈ $630,000; 3% balance ≈ $356,000
  • The 6% saver also collects the full $54,000 of lifetime match vs. $27,000 at 3%

Contributing 6% instead of 3% adds roughly $274,000 over 30 years

Below the 6% limit, every extra dollar you contribute is matched — the cheapest return available. Above the limit, contributions still grow but earn no additional match.

Starting Early

What is the cost of waiting 10 years to start saving?

Two workers each contribute 10% of a $60,000 salary with a 50%-up-to-6% match at 7%. One starts at 25 (40 years), the other at 35 (30 years), both from a $0 balance.

  • Total monthly contribution = $500 + $150 = $650
  • 40-year balance: 650 × [((1.005833)^480 − 1) / 0.005833] ≈ $1,706,000
  • 30-year balance: 650 × [((1.005833)^360 − 1) / 0.005833] ≈ $793,000
  • The extra 10 years more than doubles the result despite only 33% more contributions

Starting 10 years earlier more than doubles the retirement balance

This is compounding at work: the earliest dollars have the most time to grow, so they contribute disproportionately to the final balance.

Return Sensitivity

How much does the assumed return change the outcome?

Same saver — $10,000 start, $60,000 salary, 10% contribution, 50%-up-to-6% match, 30 years — modeled at a conservative 5% versus an optimistic 9% return.

  • Total monthly contribution = $500 + $150 = $650
  • At 5%: balance ≈ $586,000
  • At 7%: balance ≈ $874,000
  • At 9%: balance ≈ $1,337,000

A 4-point swing in return (5% → 9%) more than doubles the projected balance

Return is the single most uncertain input. Modeling a range — not a single guess — gives a more honest picture of the possible outcomes.

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