Learn
Concepts that drive your plan.
Every assumption in Calcifir is grounded in research we link out to. Each guide is interactive — play with the numbers, or sign in to see them run on your own plan.
FIRE foundations
The core ideas every plan rests on.
What is FIRE?
Financial independence, retire early — the whole idea in one place.
Your FIRE number
Annual expenses × 25 — and when that's wrong.
Why savings rate trumps income
The percentage matters more than the dollars.
The 4% rule
Bengen's foundational paper and what it actually says.
Coast FIRE
When existing savings will reach your goal without further contributions.
Flavors of FIRE
Same destination, different routes.
Spending it down
Strategies for turning savings into income.
Withdrawal strategies
Fixed real, VPW, CAPE, floor-ceiling, spending smile.
Guyton-Klinger guardrails
Dynamic withdrawals that adapt to markets.
Floor & ceiling
Cap the swings in your spending without going broke.
The retirement spending smile
Spending isn't flat — it dips then rises late in life.
Sequence of returns risk
The early-retirement risk that matters most.
Risk & returns
What the market does to your plan.
Monte Carlo
Why probability beats single-path projections.
The CAPE ratio
Valuations and what they imply for safe withdrawals.
Real vs nominal returns
Why inflation is the number that actually matters.
The drag of fees
How a 1% fee costs you years of retirement.
Lifestyle creep
How rising spending pushes your FIRE date away.
Taxes & accounts
Keep more of what you withdraw.
Account types
Pre-tax, Roth, taxable, HSA — and when to use each.
Tax-efficient withdrawal
The order you tap accounts changes your tax bill.
The Roth conversion ladder
Tax-free withdrawals before 59½.
The HSA triple advantage
The only triple-tax-free account, and how to use it.
Self-employed accounts
Solo 401(k), SEP-IRA — bigger limits when you work for yourself.
Retirement income
The streams that fund the gap.