Coastline vs cFIREsim
cFIREsim is a beloved historical-cycle simulator for testing retirement withdrawal strategies. Coastline covers the whole journey — building wealth and spending it — with real US/Canada tax math and a full breakdown of every number. They overlap, but they’re built for different questions.
Coastline vs cFIREsim, feature by feature
| Coastline | cFIREsim | |
|---|---|---|
| Free, no signup | Yes | Yes |
| Historical-cycle / Monte Carlo simulation | Yes | Yes |
| Accumulation (working years) modeling | Yes | No |
| Federal + state income tax math | Yes | Limited |
| Roth conversion / withdrawal-order strategy | Yes | No |
| Social Security claim-age modeling | Yes | Basic |
| Canada (CPP/OAS, RRSP/TFSA) | Yes | No |
| Shows the exact math behind every number | Yes | No |
| Save / share scenarios by link | Yes | Limited |
When to use cFIREsim
Reach for cFIREsim when your question is purely "would my withdrawal strategy have survived history?" — it shines at running a spending plan against every historical market cycle and showing the range of outcomes. If you’re already retired or near it and want a fast historical stress-test, it’s excellent and time-tested.
When to use Coastline
Use Coastline when you want the full picture: how your wealth builds during your working years, the taxes you’ll actually pay in both accumulation and retirement, Roth-conversion and withdrawal-order strategy, Social Security timing, and — uniquely — a click-through breakdown of the math behind every figure. It also handles Canadian plans (CPP, OAS, RRSP, TFSA), which most US tools ignore.
Both tools are free. This comparison is written by Coastline, so weigh it accordingly — try both and use whichever answers your question. cFIREsim is a well-regarded tool; the differences below are about focus, not quality.
Common questions
Is cFIREsim or Coastline more accurate?
They answer different questions. cFIREsim is a rigorous historical-cycle backtester for withdrawal strategies. Coastline models the full tax and accumulation picture and shows its work. For a withdrawal-only stress test, cFIREsim is purpose-built; for whole-plan tax-aware modeling, Coastline goes further.
Are both really free?
Yes. Both are free to use. Coastline requires no account or signup and never stores your inputs on a server.
Does Coastline do historical simulation like cFIREsim?
Yes — Coastline’s Simulation Tools replay real historical market sequences (and Monte Carlo draws) to stress-test your plan, in addition to the year-by-year deterministic projection.