About Real Fire Calculator

Real Fire Calculator is an independent, one-person project built and maintained bySambhav Saxena, a software engineer. It is a free FIRE calculator and a growing library of writing about financial independence and early retirement, and it exists because most of the calculators available stop at a shortcut and call it a plan.

The problem it was built to solve

The standard advice is to multiply your annual expenses by 25. That shortcut comes from the 4% rule, which comes in turn from research testing withdrawal rates over30-year retirements. It is a reasonable approximation for someone stopping work at 65. It is the wrong tool for someone stopping at 45 and funding forty-five years, and it is silent on almost everything that happens over a real timeline: raises, inflation, a wedding or a house along the way, and a more cautious portfolio once you have actually stopped earning.

This tool was built to close that gap. It sizes your target from your own retirement horizon and return assumptions rather than a fixed multiple, compounds your contributions with a realistic annual step-up, funds one-time goals from the same plan instead of a separate spreadsheet, and uses your safe withdrawal rate as a safety cap rather than as the definition of your number. Every formula is documented on themethodology page, including the things the model deliberately does not do.

What you will find here

• The calculator — a live FIRE calculator covering the full spectrum from lean to fat, with a wealth trajectory, milestones and a breakdown of exactly what makes up your number.
• Guides — in-depth writing on the mechanics: how to calculate a FIRE number properly, where the 4% rule breaks for early retirees, sequence of returns risk, Coast and Barista FIRE, inflation, and withdrawal strategies. Every worked example uses the same engine the calculator runs on.
• Methodology — every formula, assumption and limitation, written out.
• Glossary — plain-English definitions of the terms the rest of the site assumes.

Editorial standards

The writing here follows a few rules, and it is fair for you to hold the site to them:

• Every number is reproducible. Worked examples state their assumptions and use the same calculation engine as the tool, so you can reproduce any figure on the site by entering the stated inputs yourself.
• Limitations are stated, not buried. The model ignores taxes, market volatility, pension income and spending curves. That list lives at the top of the methodology page rather than in a footnote, because knowing what a model excludes is part of knowing what its output means.
• No predictions are sold as facts. Default rates are illustrative starting points chosen to be defensible, and every one of them is editable.
• Corrections are made in public. If something here is wrong, it gets fixed and the guide's "updated" date changes. Methodology corrections are the most useful feedback this project receives — pleasesend them.

How it is funded, and why it is free

There is no signup, no email gate and no paywall, and there is not going to be one. The site is supported by display advertising, which is why you may see ads on these pages. Advertising has no influence on the content: there are no sponsored guides, no affiliate links, and no products or services being sold to you here.

The calculator runs entirely in your browser. The figures you enter — your income, savings, expenses and goals — are never sent to a server, stored, or logged, because there is no server-side component to the calculation at all. Theprivacy policy sets out exactly what the site does collect, which is analytics and advertising data unrelated to your inputs.

What this is not

This calculator is not financial advice, and it is not built or reviewed by a licensed financial advisor. It is a modelling tool: it takes assumptions you provide — a return rate, an inflation rate, a withdrawal rate, a life expectancy — and projects them forward deterministically. Real markets do not move in straight lines, tax rules vary by country and by account, and nothing here knows anything about your circumstances.

Treat the output as a way to reason about trade-offs and test the sensitivity of a plan to its assumptions, not as a guarantee or a recommendation. For decisions that matter, talk to a qualified professional in your own jurisdiction. The fullterms and conditions set out the disclaimer in detail.

Feedback

Found a bug, a confusing assumption, or a feature this calculator is missing?Get in touch. As a solo project, every bit of feedback directly shapes what gets built next.