Calculator Servicescalculatorservices.com
Financial

401(k) Calculator

401(k) projection with employer match. Free online 401(k) Calculator. Calculate 401(k) online — fast, accurate, mobile-friendly, no signup needed.

Final balance
$1,138,639.60

Derivation

  1. ├── 01Givensalary = 80000, pct = 10, match = 4, r = 7, n = 30
  2. ├── 02Formulat × (a+n) / 100 / 12 × ((1+r / 100 / 12)^(12 × o)-1) / (r / 100 / 12)
  3. ├── 03Substitutet × (a+30) / 100 / 12 × ((1+7 / 100 / 12)^(12 × o)-1) / (7 / 100 / 12)
  4. └── 04Compute Final balance$1,138,639.60
Did you know?

The US 401(k) exists because of a single 1978 tax-code subsection (section 401(k)) that accidentally allowed tax-deferred salary deferrals.

§01What is

Understanding the 401(k) Calculator

The 401(k) Calculator computes Final balance from 5 inputs: salary ($), you contribute (%), employer match (%), return (%), years. 401(k) projection with employer match.

Quick calculators for the math that shouldn’t need a notepad — instant, accurate, private to your browser. The 401(k) Calculator sits in that toolkit — it 401(k) projection with employer match. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

t × (a+n) / 100 / 12 × ((1+r / 100 / 12)^(12 × o)-1) / (r / 100 / 12)

Where

salary
Salary ($)
pct
You contribute (%)
match
Employer match (%)
r
Return (%)
n
Years
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Salary ($) = 80000, You contribute (%) = 10, Employer match (%) = 4, Return (%) = 7, Years = 30.

  1. 01Start by noting the input — Salary ($): 80000.
  2. 02Start by noting the input — You contribute (%): 10.
  3. 03Start by noting the input — Employer match (%): 4.
  4. 04Start by noting the input — Return (%): 7.
  5. 05Start by noting the input — Years: 30.
  6. 06Substitute these values into the formula: t × (a+n) / 100 / 12 × ((1+r / 100 / 12)^(12 × o)-1) / (r / 100 / 12)
  7. 07Compute Final balance: the calculator returns 1138640.
  8. 08Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common 401(k) Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Salary ($) halved

salary = 40000 (from 80000)

Keep every other input at its default and halve the salary ($). See how final balance responds.

  1. 01New Salary ($): 40000
  2. 02Baseline Final balance: 1138640
  3. 03New Final balance: 569320
  4. 04Final balance decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Salary ($) doubled

salary = 160000 (from 80000)

Keep every other input at its default and double the salary ($). See how final balance responds.

  1. 01New Salary ($): 160000
  2. 02Baseline Final balance: 1138640
  3. 03New Final balance: 2277280
  4. 04Final balance increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

You contribute (%) halved

pct = 5 (from 10)

Keep every other input at its default and halve the you contribute (%). See how final balance responds.

  1. 01New You contribute (%): 5
  2. 02Baseline Final balance: 1138640
  3. 03New Final balance: 731983
  4. 04Final balance decreases by 35.7% → use this sensitivity to plan for real-world variation.
04 · PATTERN

You contribute (%) doubled

pct = 20 (from 10)

Keep every other input at its default and double the you contribute (%). See how final balance responds.

  1. 01New You contribute (%): 20
  2. 02Baseline Final balance: 1138640
  3. 03New Final balance: 1951950
  4. 04Final balance increases by 71.4% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
Your feedback

How useful was this calculator?

Your ratings stay in your browser — they help us learn which tools people actually rely on.

Rate it
Was this helpful?