Retirement Calculator Comparison: Scenarios vs FICalc, cFIREsim, ProjectionLab, Boldin, Guiide, and RetireEasy

The Short Answer

Scenarios is the only UK-focused retirement calculator that runs a full 1,000-simulation Monte Carlo model against your actual UK tax position. FICalc.app, cFIREsim, and FIRECalc are free US tools that replay historical US market returns and don't model tax at all. ProjectionLab, Boldin (formerly NewRetirement), and Empower's Personal Dashboard are broader US financial-planning tools built around US tax brackets and account types. Guiide and RetireEasy are UK-facing, but work by comparing a handful of hand-built scenarios rather than a full probability distribution. MoneyHelper's calculator is a simple, free, non-simulation tool from the UK government.

For a UK saver who wants a genuine probability of success, calculated against real UK Income Tax, Capital Gains Tax, and pension rules rather than a US approximation or a single hand-picked scenario, Scenarios is the only tool on this list built to do that.

How Does Scenarios Compare to FICalc, cFIREsim, ProjectionLab, and Others?

One caveat that applies to every row except Scenarios: I don't have access to these tools' source code, so this is drawn from public documentation and normal use, not verified internals. Check each vendor's site for their current feature set.

Why Choose Scenarios Over FICalc, ProjectionLab, Guiide, or RetireEasy?

FICalc and its historical-replay cousins are genuinely good at what they do; free, well-established, purpose-built for US sequence testing. But none of the other nine tools here combine what Scenarios does in one place:

• A full UK tax engine, not an approximation. Income Tax bands, including the Scottish variant and the 60% effective marginal rate between £100,000 and £125,140 caused by personal allowance taper, Capital Gains Tax with real cost-basis tracking per account, dividend and savings income tax, and the pension rules that actually govern UK drawdown (Annual Allowance, Money Purchase Annual Allowance, Lump Sum Allowance).
• A tax-optimised withdrawal order. Every simulated year runs a seven-tier waterfall: guaranteed income first, then tax-free cash, then pension income up to the personal allowance, then ISA, then remaining pension, then GIA, then cash, closer to how a well-run UK retirement is actually drawn down than a flat percentage split.
• Correlated asset returns, not independent ones. Seven asset classes are generated through a calibrated correlation matrix via Cholesky decomposition, so the diversification benefit of a mixed portfolio comes from the maths rather than an assumption.
• Dynamic spending strategies, tested against a fixed one. Guyton-Klinger guardrails and floor/ceiling spending both sit alongside the default fixed real withdrawal, with every threshold editable.
• A stricter bar for success. A plan only counts as funded if it meets the spending target in every single year, not just "didn't hit zero by the end."
• A reproducible answer. The random seed comes from a hash of your plan's inputs, so the same plan always returns the same result, ruling out re-running until a preferred number shows up.
• Published methodology. Every assumption is documented on the methodology page and walked through in full in What's Inside a Scenarios Simulation, including what the model doesn't capture. The mechanics behind the simulation engine itself are covered in Understanding Monte Carlo Simulations.

Is Scenarios Free Like FICalc?

Scenarios' free tier includes the core Monte Carlo simulation, fan chart, and median wealth projection, the same category of output the free US tools give you, at the same price. Full tax precision, the withdrawal strategy optimiser, and couple modelling sit on paid plans from £72/year. Full detail is on the pricing page.

This is methodology, not financial advice, and Scenarios isn't authorised to provide regulated advice. You can build a free plan and see how your own numbers hold up against a full UK tax position.