Typed 401l? The l and k sit side-by-side on the keyboard — you’re in the right place for a free 401(k) calculator.

About 401lcalculator.com

We are an independent retirement planning tool platform for U.S. workers — not a broker, not a wealth manager, and not a stock-picking site. Every calculator publishes its assumptions, enforces IRS contribution rules where relevant, and runs locally in your browser so your inputs never leave your device.

  • Reviewed by David Jones
  • Limits Updated for 2026 IRS caps
  • Formulas Verified quarterly

Last reviewed: .

DJ

David Jones

  • Founder of 401lcalculator.com
  • Retirement Planning Tool Researcher
  • Calculator Methodology Specialist

David builds and maintains the calculators on this site from Juneau, Alaska. The work is calculator research: translating IRS retirement-plan rules, employer match formulas, and savings-projection math into tools that ordinary workers can run without signing up or handing over account data.

He does not provide individualized investment recommendations, portfolio management, or stock analysis. The site exists so you can model deferrals, match, limits, withdrawals, and long-run balances with transparent assumptions.

Contact: [email protected] · contact form

What we research (and what we ignore)

Our research focus stays narrow on purpose:

  • Retirement planning tools — paycheck deferrals, match capture, catch-up bands, and balance projections.
  • Calculator methodology — how each input maps to IRS rules and plan-language examples.
  • IRS contribution systems — elective deferral caps, Section 415(c) totals, SECURE 2.0 age bands, and RMD framing.
  • Savings projections & employer match logic — tiered match, true-ups, per-paycheck splits, and inflation-adjusted outputs.
  • Retirement forecasting — educational scenarios, not trading signals.

We do not publish stock picks, fund ratings, or wealth-management pitches. If a page mentions market returns, it is only as a user-adjustable assumption inside a projection tool.

Calculator methodology

Every major tool follows the same pipeline:

  1. Define the worker question (e.g., “How much per paycheck to max out?” or “What is my employer match in dollars?”).
  2. Extract rules from primary sources — IRS notices, Publication 560, Treasury/SECURE 2.0 summaries, and SSA tables when relevant.
  3. Encode the rule in JavaScript with explicit caps, age gates, and plan-style examples documented on the page.
  4. Publish defaults (return, inflation, salary growth) that you can change — never hidden inside a black box.
  5. Cross-check outputs against hand-calculated scenarios and, where applicable, sibling tools on this site.

Employer match logic

Simple and tiered match formulas are modeled separately. We document cap percentages and show annual match dollars, not just “50% up to 6%.”

IRS limit enforcement

Deferral, catch-up, super catch-up, and combined 415(c) ceilings are applied in code and explained in plain English on the limits reference page.

Retirement forecasting

Long-run balances are compound-growth projections with optional inflation adjustment. They illustrate savings paths, not market forecasts.

Privacy-first execution

Inputs stay in your browser. We do not operate accounts, store salary data, or sell leads to advisors.

Calculator testing process

  • Quarterly formula review. Core match, deferral, tax-bracket, and growth paths are re-tested on a fixed scenario matrix (documented internally and spot-checked on each tool page).
  • Regression checks when logic changes. If one calculator shares code with another (for example, limits in the flagship 401(k) model), both are re-run before publish.
  • Edge-case passes. Zero salary, maxed deferrals, catch-up ages, and separation ages are tested so the UI does not silently return misleading zeros.
  • Mobile usability. Tools are checked on small screens because most workers run paycheck math on a phone.

IRS update process

IRS dollar limits are not guesswork on this site:

  • Annual notice window. Within 30 days of the IRS publishing new 401(k) limit figures, we update the limits reference page and every calculator that enforces caps.
  • Mid-year rule changes. When SECURE 2.0 or Treasury guidance changes calculator logic (RMD ages, catch-up bands, etc.), we update affected tools and note the change on the relevant guide.
  • Source hierarchy. IRS publications beat secondary articles. Your plan document beats our generic model when the two conflict.

Official starting point: IRS Retirement Topics — 401(k) limits.

Independence & transparency

  • No broker partnerships and no paid placement of financial products.
  • Monetization: optional Google AdSense display ads only.
  • Not licensed advice. For tax filing, plan elections, or retirement planning specific to your household, use a qualified professional.
  • Corrections welcome. Email [email protected] with a primary source link; we aim to respond within five business days.

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