Fidamen

Safe Withdrawal Rate Calculator

This calculator helps estimate sustainable retirement withdrawals using multiple methods: fixed-rate, inflation-adjusted, a rule-of-thumb benchmark, and a Monte Carlo heuristic. Use the controls to compare outcomes and understand trade-offs between simplicity and model complexity.

Results are intended as guidance, not guarantees. The tool includes conservative heuristics and exposes the parameters that matter most: portfolio value, spending, expected returns, inflation, and volatility.

Updated Nov 6, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 68d41ecd3594 • Reviewed by Fidamen Standards Committee

Start with a withdrawal percentage, then index the withdrawn amount to inflation each year. Useful when you want spending power maintained in real terms.

Inputs

Advanced inputs

Monte Carlo options

Results

Updates as you type

First-year withdrawal

$40,000.00

Required portfolio for target spending

$1,000,000.00

OutputValueUnit
First-year withdrawal$40,000.00USD
Required portfolio for target spending$1,000,000.00USD
Primary result$40,000.00

Visualization

Methodology

Fixed-rate: multiplies portfolio value by the chosen withdrawal percentage to produce a first-year withdrawal.

Inflation-adjusted: computes the first-year withdrawal from a rate and shows the portfolio required to support a target first-year spending; subsequent years are indexed to the inflation assumption to preserve spending power.

Rule-of-thumb: a flat benchmark (4%) provided for quick comparison; treat it as a heuristic rather than a guaranteed safe rate.

Monte Carlo heuristic: when full simulation is not available, we estimate a conservative sustainable rate using expected real return minus a volatility buffer. Full Monte Carlo simulation (many stochastic paths) is recommended for deeper analysis and requires a computational engine.

Key takeaways

Compare methods to see the sensitivity of withdrawal outcomes to key assumptions.

Consider running full Monte Carlo simulations with a dedicated engine for scenario probabilities and sequence-of-returns risk analysis.

Adjust assumptions conservatively and revisit plans periodically as markets and personal circumstances change.

Worked examples

Example 1: $1,000,000 portfolio, 4% withdrawal → first-year withdrawal = $40,000.

Example 2: $800,000 portfolio, target $50,000 spending, chosen rate 5% → required portfolio = $50,000 / 0.05 = $1,000,000 (shows shortfall).

Example 3 (heuristic): expected return 6%, inflation 2% → expected real return 4%. With volatility 12%, heuristic SWR ≈ 4% - (12% / 4) = 1% (very conservative).

F.A.Q.

Is the 4% rule always safe?

No. The 4% rule is a long-used benchmark for a 30-year retirement in historical US-market conditions. Safety depends on horizon, returns, inflation, sequence-of-returns, taxes, and spending flexibility.

What does the Monte Carlo heuristic mean?

It provides a conservative approximate withdrawal rate based on expected real return minus a volatility buffer. For a probability-based answer you must run full stochastic simulations.

How accurate are these estimates?

Estimates are approximate. Numerical results depend on input assumptions and model choice. For computational reproducibility, follow numerics best practices (IEEE floating-point considerations) and validate simulations against independent engines.

Should I rely only on this calculator?

Use this tool for initial planning and comparison. For legally binding financial advice, tax, or regulatory decisions consult a licensed professional.

Sources & citations

Further resources

External guidance

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 68d41ecd3594

What changed (latest)

v1.0.0 • 2025-11-06 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 6, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-06 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: adcfe1645b0c