Top 5 FIRE Calculators UK 2026
Five calculators compared. Only one is built for UK rules (state pension timing, the ISA bridge and the 25% tax-free lump sum) and works from your real accounts, not typed guesses. See your FI date.
A Practitioner Perspective
Most FIRE calculators are American. They don't know the state pension exists, they can't model the gap between early retirement and pension access, and they have never heard of an ISA. I tested the ones UK savers actually use. The short version: a number you typed into a calculator is only as good as your typing. What matters is whether the plan behind it holds.
Summary: Top 5 FIRE Calculators in the UK
| Tool | Best For | Pricing | Free Tier | UK-Specific | Rating |
|---|---|---|---|---|---|
| Delphina | A UK-specific FI date built from your real accounts | Free tier / From £9.99/mo | ✓ | ✓ | ★★★★★ |
| ProjectionLab | DIY FIRE planning with Monte Carlo simulations | Free tier / Plus from $9/mo | ✓ | ✗ | ★★★★★ |
| Open Money | UK-focused cashflow planning for FIRE seekers | From £6/mo | ✗ | ✓ | ★★★★★ |
| Boldin (formerly NewRetirement) | Detailed retirement income planning | Free tier / Plus from $108/yr | ✓ | ✗ | ★★★★★ |
| Vanguard Retirement Calculator | UK pension-aware retirement planning | Free (with Vanguard account) | ✓ | ✓ | ★★★★★ |
Get your FI date from your real numbers
UK state pension, ISA bridging and the 25% tax-free lump sum, built in. Add your actual pensions and ISAs so the projection starts from the truth rather than an estimate.
What Makes a Good FIRE Calculator
Not all FIRE calculators are created equal. After testing dozens of options, here is what separates the genuinely useful from the merely interesting.
- Realistic projections: Uses sensible return assumptions rather than optimistic averages that ignore sequence-of-returns risk
- Complete financial picture: Connects to all your accounts, pensions, investments, and property for an accurate starting point
- Scenario flexibility: Allows you to model different savings rates, retirement ages, and spending levels in retirement
- UK-specific considerations: Accounts for UK State Pension, workplace pension contributions, and relevant UK tax wrappers
- Actionable insights: Not just a number, but specific guidance on what changes would have the biggest impact
The 5 Best FIRE Calculators in the UK
Delphina
See your FI date →Know where you are. Change where you are going.
Delphina is built around the UK specifics the US calculators miss: state pension timing, the ISA bridge between early retirement and pension access, and the 25% tax-free lump sum. Rather than projecting from numbers you type, it brings together your real pensions, ISAs and accounts so the FI date starts from the truth, and keeps updating as markets move and contributions change. A free tier covers the projection itself.
See your UK FI number
Adjusted for state pension, ISA bridging, and 25% pension tax-free lump sum. Not a US spreadsheet.
Calculate my FI numberProjectionLab
Visit ProjectionLab→Build Financial Plans You Love
ProjectionLab is a powerful DIY financial and retirement planning tool built by FIRE enthusiasts. It enables users to build living financial models with Monte Carlo simulations, Sankey diagrams for cash flow visualisation, detailed tax analytics and net worth tracking over time. Supports UK-specific account types like ISAs, workplace pensions, and SIPPs.
Open Money
Visit Open Money→Plan, project, prepare
Open Money is a UK-built cashflow planning tool aimed at individuals who want to understand their financial future without going through a financial adviser. Projects forward over 10–30 years and accounts for UK-specific tax wrappers including ISAs, pensions and the state pension: exactly what FIRE calculations need.
Boldin (formerly NewRetirement)
Visit Boldin (formerly NewRetirement)→The most powerful retirement planner
Boldin (formerly NewRetirement) is a comprehensive DIY retirement planner with detailed income and expense modelling and scenario comparisons. Strong for FIRE-adjacent users who want to model withdrawal strategies and healthcare costs in retirement.
Vanguard Retirement Calculator
Visit Vanguard Retirement Calculator→Plan your retirement journey
Vanguard offers a retirement calculator that is well-suited to UK investors, taking into account UK State Pension entitlements alongside workplace and private pensions. It projects whether your retirement savings will provide adequate income and allows you to model different contribution levels and retirement ages.
A Number vs a Plan
Every FIRE calculator on this list is a projection tool: that is the whole point of the category. The honest distinction is not what they project. It is what they project from.
A calculator projects from what you type. Assumed savings rate, assumed return, assumed spending. It gives you a number, and the number is only as good as your typing. Most people's inputs flatter them: the pension they guessed at, the spending they rounded down.
A plan projects from what you actually hold. Delphina brings together your real pensions, ISAs and accounts, so the projection starts from the truth rather than the estimate. And it keeps running: markets move, contributions change, and the answer updates instead of going stale in a browser tab.
A number is easy. Knowing whether it holds is the hard part.
What Delphina Is Not
If all you want is a rough number from figures you type in yourself, any calculator on this list will give you one, and a spreadsheet will too. That is not what Delphina is for.
Delphina the platform is a different tool for a different moment: when you want to know whether the plan behind your number actually holds. It brings together your real accounts, models the awkward years between FIRE and pension access, and shows which changes move your date most. It is not a spreadsheet replacement and it is not regulated financial advice.
A number is easy. Knowing whether it holds is the hard part.
Conclusion
The right tool depends on where you are. For DIY modelling with Monte Carlo simulations, ProjectionLab is the FIRE community's favourite for a reason. For UK-built cashflow planning, Open Money is solid. Boldin (formerly NewRetirement) suits detailed retirement income modelling if you can live with manual UK entry, and Vanguard's calculator is a sensible free check if you hold your investments there.
But if you want a FI date you can actually act on, see yours in Delphina. It is UK-specific, built from your real pensions and ISAs, and it keeps updating instead of going stale in a browser tab.
A calculator gives you the number. The plan behind the number is the part that has to hold. When you are ready to test that, Delphina is built for it.
You Have the Number. Does the Plan Behind It Hold?
The calculator told you when. Delphina brings together your real pensions and ISAs and tells you whether, and what would move the date.