The Savings Rate Is Everything: How One Number Controls Your FIRE Date

The single most important table in FIRE

Mr Money Mustache published it in 2012, and it's the most important chart in personal finance:

| Savings rate | Years to FI | |---|---| | 10% | ~51 | | 20% | ~37 | | 30% | ~28 | | 40% | ~22 | | 50% | ~17 | | 60% | ~13 | | 70% | ~8.5 | | 80% | ~5.5 |

Assumptions: 5% real investment returns, 4% safe withdrawal rate, you start from zero.

The table is mathematically clean. As your savings rate rises, three things happen at once:

1. You add more to your portfolio each year.
2. Your required FIRE number falls (because you spend less).
3. Both effects compound.

A 10% savings rate means you spend 90% of income and save 10%. To replace that 90% spend forever at 4%, you need 22.5 years of income saved up. With low savings, your portfolio takes forever to grow there. A 70% rate flips it: you only need 7.5 years of income saved, and you're saving 7× as much per year.

Why income matters less than you'd think

Two people, both at a 30% savings rate:

• Person A: earns £40k, saves £12k, spends £28k → FIRE number £700k → ~28 years
• Person B: earns £200k, saves £60k, spends £140k → FIRE number £3.5m → ~28 years

Same time to FI. The income difference cancels out because higher income usually means higher expenses, which means a bigger FIRE number.

The only way income helps is if it doesn't cause expense inflation. The classic FIRE move: pay rises go straight to savings, not lifestyle. That converts an income increase into a savings-rate increase, which is where the leverage lives.

How to actually raise your savings rate

Three categories of move, ranked by typical impact:

The big three (each can shift your rate by 5–15%):

• Housing — buy small, rent low, geographically arbitrage
• Transport — one car or none, drive cheaper used vehicles
• Lifestyle creep — pre-commit raises to savings before they hit your account

The middle five (each can shift by 1–3%):

• Tax efficiency — max ISA, SIPP, salary sacrifice (UK), 401k, HSA (US)
• Investment fees — switch from 1% advisor fees to 0.1% DIY
• Insurance optimisation — shop home, car, life every few years
• Subscriptions audit — kill what you don't use
• Cash management — high-yield accounts for emergency funds

The small but cumulative (1% combined):

• Cooking instead of eating out
• Energy efficiency
• Buying things used
• Cashback / credit card rewards

Don't optimise the small stuff before the big stuff. Cutting your coffee budget while paying £2,000/month for a too-big flat is the opposite of leverage.

The honest catch

The Mr Money Mustache table assumes you can sustain the savings rate. For most people, 70%+ is only possible by either:

• Earning unusually high and not inflating lifestyle
• Living unusually frugally
• Both

50% is a more realistic stretch goal for high earners; 30–40% is excellent for typical household incomes. Going from 30% to 40% takes 6 years off your FIRE date. From 40% to 50% takes 5 more. The leverage on each marginal percentage point is enormous.

Track it, don't optimise it once

Your savings rate isn't a one-time calculation. Track it monthly:

• (Pre-tax income − all spending) / pre-tax income

Use the same denominator every month so you're comparing like with like. Watch the trend. Raise it slowly. Watch the time-to-FI shrink in real time.

Our simulator takes your savings rate and current portfolio as inputs and shows the FI date distribution across every historical sequence — it's a more honest answer than any static table can give.