About RetireBy
RetireBy is a free, no-signup UK FIRE calculator and education resource. We built it because the best FIRE tools were mostly American, and UK-specific calculators that properly handle the state pension, pension access ages, and ISA/SIPP structure were hard to find.
Our goal: Give you the tools to find your number — your personal FIRE number — and understand exactly what you need to do to get there.
What We Cover
- Simple FIRE calculator — enter your spending, pot, and savings rate; see your FIRE number and how long it takes to get there
- Advanced retirement calculator — year-by-year modelling of SIPP/ISA drawdown, UFPLS tax rules, state pension, DB pension, and UK income tax; finds your earliest viable retirement age
- Savings rate calculator — the single most important variable in your FIRE journey
- Coast FIRE calculator — find out if your pot is already self-sustaining
- Guides — on the 4% rule, Lean FIRE, Fat FIRE, Barista FIRE, ISA vs SIPP strategy, and the state pension
Our Approach
Everything on this site is built around UK-specific numbers:
- State pension of £11,502/yr from age 67 (current 2024/25 rate)
- Pension access rules (57 from 2028)
- ISA allowance (£20,000/yr)
- UK income tax: Personal Allowance £12,570, basic rate 20%
All growth rates are entered in real terms (after inflation), so the numbers you see are in today’s money. Every assumption is adjustable.
Author
RetireBy is written and maintained by a UK private investor who went through the FIRE planning process the hard way — with US-centric tools that didn’t properly account for state pension, pension access restrictions, or ISA strategy.
The calculators are built to be transparent and honest. We show working, explain assumptions, and let you adjust everything that matters.
E-E-A-T: Our Expertise
This site covers financial planning concepts, not personalised financial advice. We apply:
- Experience: Personal UK FIRE journey with real money decisions
- Expertise: Financial mathematics, UK pension rules, tax-efficient investing
- Authoritativeness: Sources cited, calculations explained, assumptions visible
- Trustworthiness: No paywalls, no required email, clearly disclosed affiliate relationships
Affiliate Relationships
We may earn a commission if you open an investment account through our links — at no cost to you. This helps keep the calculators free. We only feature platforms we’d genuinely consider using ourselves: AJ Bell, Hargreaves Lansdown, Vanguard, Trading 212, and InvestEngine.
Our editorial content is not influenced by affiliate relationships. The calculators give you the same result regardless of which platform you use.
Disclaimer
Nothing on RetireBy constitutes financial advice. The calculators are educational tools to illustrate possibilities based on the assumptions you enter. Past market performance is not a guide to future returns. Always consider seeking regulated financial advice for major retirement planning decisions.