How we calculate · 401(k)

How the 401(k) calculator works

Clear contribution math for learning—not investment advice.

Written & maintained by John Rey Balais Developer · Nestfigure

Tool: 401(k) calculator · Embed · All how-we-calculate pages · Questions

Purpose

Estimate annual employee deferral and employer match under a simple teaching formula, plus an optional multi-year balance at a constant return sample you type. Educational only.

Annual contributions

Employee: salary × (employee% / 100)
Match window: salary × (matchUpTo% / 100)
Employer match: min(employee, matchWindow) × (matchRate% / 100)
Match left on table: max employer if full window − actual employer match

Optional growth

For each year: add that year’s total contribution to the balance, then multiply by (1 + annualReturn%). This is a teaching model—not monthly payroll timing or rebalancing.

What we intentionally leave out

IRS contribution limits, catch-up, and mega backdoor math
Vesting schedules, true-up, and multi-tier match formulas
Taxes, Roth vs traditional, and required minimum distributions
Live market returns, fees, and fund recommendations

Last reviewed: August 9, 2026.

YMYL notice: This site is for education only. It is not financial, tax, or investment advice. Nestfigure is not a bank, credit union, broker, investment adviser, or fiduciary. Product terms, rates, and penalties vary—always read your institution’s disclosures before acting. Calculator results are mathematical estimates, not bank quotes.