The Two-Tool Stack for Retirement Planning: Why You Need Free + Paid

Every “best retirement planning software” listicle on the open web reviews tools in isolation: pick one, sign up, done. That framing is wrong — and it’s wrong because the affiliate model rewards single-product reviews. The truth, visible to anyone who’s actually used these tools, is that most serious DIY retirement plans use two tools, not one.

Here’s why.

Why two tools, not one

The free Monte Carlo tools (FIRECalc, cFIREsim, Engaging Data, ProjectionLab free tier) are better at probability-of-success modelling than most paid tools. They’re built by retirement-math nerds, not product managers chasing feature parity. FIRECalc runs every historical return sequence since 1871. That’s a simulation depth that paid tools at $120/yr don’t match for historical testing.

The paid tools (Boldin PlannerPlus, Maxifi) are better at year-by-year tax optimisation, Roth conversion sequencing, and IRMAA/Medicare premium projection — because they have the engineering investment to track tax-code changes and model complex multi-account interactions.

A serious plan uses both:

• The free tool answers: “Do I have enough, and what is my probability of success?”
• The paid tool answers: “What should I do this year to optimise taxes, and in what order should I draw down accounts?”

Recommending a single tool for both jobs is like recommending one tool for both structural engineering and interior design. They’re different jobs.

The two-tool stack by segment

Segment 1: Mid-career DIY modeler (35-55, actively saving)

Free tool: ProjectionLab free tier or FIRECalc Paid tool: Boldin PlannerPlus ($120/yr)

Order of operations:

1. Start in ProjectionLab free — build the basic model (savings, income, expenses, target retirement age). Run Monte Carlo. Get a baseline probability of success.
2. If probability is above 80% and you’re within 15 years of retirement: open Boldin PlannerPlus. Add Roth conversion planning. Model the tax bracket targeting for each year between now and retirement. Model the IRMAA cliff if your income is above $103K single / $206K married.
3. Annually: update both tools with actual numbers. Use ProjectionLab for the “are we still on track?” answer. Use Boldin for the “what should we do with our taxes this year?” answer.

Estimated cost: $0 (free tools only) to $120/yr (add Boldin). For most mid-career planners with straightforward tax situations, the free tools alone are sufficient until you’re within 10 years of retirement.

Segment 2: Pre-retiree (5-10 years from retirement)

Free tool: FIRECalc Paid tool: Boldin PlannerPlus ($120/yr)

Order of operations:

1. Build the full model in Boldin PlannerPlus: model the Roth conversion window between now and Social Security / RMD start. Model healthcare gap (if retiring before Medicare at 65). Model IRMAA implications of Roth conversions.
2. Run the same scenario in FIRECalc as an independent sanity-check. FIRECalc’s historical sequence testing is independent of Boldin’s Monte Carlo — two independent methods agreeing on a success probability is more reliable than one.
3. If Boldin says 88% and FIRECalc says 85%, you have a convergent view. If they diverge significantly, investigate why (different asset allocation assumptions, different horizon assumptions).

Why this segment especially needs two tools: The Roth conversion window (retirement to RMD) is the highest-stakes optimisation window in DIY retirement planning. Boldin models it better than any free tool. But using only Boldin means you have only one Monte Carlo simulation (1,000 runs). FIRECalc’s historical testing gives you an independent second view.

Estimated cost: FIRECalc ($0) + Boldin PlannerPlus ($120/yr) = $120/yr total. At this life stage, this is the best-spent $120 in your financial life.

Segment 3: FIRE pursuer (any age, targeting early retirement)

Free tool: cFIREsim or FIRECalc (historical) + ProjectionLab free (Monte Carlo) Paid tool (optional): ProjectionLab Premium ($109/yr) or Boldin PlannerPlus ($120/yr)

Order of operations:

1. Start with FIRECalc and cFIREsim — the FIRE community standards for historical sequence testing. Run your scenario through every historical starting year. If you survive 1929, 1966, and 2000, you have meaningful historical confidence.
2. Cross-check with ProjectionLab free (Monte Carlo) for scenarios not in the historical record (tail risks beyond what history shows).
3. When within 15 years of target FIRE date: add Boldin PlannerPlus for the Roth conversion ladder modelling. FIRE planners often have an extended low-income window before Social Security — this is a large Roth conversion opportunity that needs specific tax modelling.

Why the FIRE segment is different: The 30-60 year horizon means sequence risk compounds significantly. Historical testing (FIRECalc) and Monte Carlo (ProjectionLab) both have important roles. Neither alone is sufficient.

Estimated cost: $0 (free tools alone) is sufficient for the “do I have enough?” question. Add Boldin ($120/yr) when you need the Roth conversion optimisation layer.

Segment 4: High earner (HENRY, above $200K household income)

Free tool: FIRECalc (historical sanity check) Paid tool: Boldin PlannerPlus ($120/yr) or Maxifi Planner ($149-$309/yr)

Order of operations:

1. If your situation involves megabackdoor Roth, deferred comp, NUA on company stock, or multiple complex equity compensation types: use Maxifi. The economic lifecycle model handles multi-account stacking better.
2. For everything else: Boldin PlannerPlus covers the Roth conversion, IRMAA modelling, and multi-account drawdown depth that high earners need.
3. Add FIRECalc as the independent historical sanity check.

At above $500K household income: consider Boldin Advisors ($2,800 flat fee) — a one-off CFP consultation using your Boldin model. At this income level, the EV of a professional review is high.

Estimated cost: $120-$309/yr for the paid tool layer. The tax optimisation EV at this income level (Roth conversions alone can save $20,000-$100,000+ in lifetime taxes) makes this among the highest-ROI software subscriptions available.

Common mistakes with single-tool planning

Mistake 1: Trusting only the free tool Free linear calculators (Fidelity, Vanguard, Bankrate) show “you’re on track” without Monte Carlo. A plan showing “on track” in these tools has roughly a 60-70% success probability in Monte Carlo. That is not the same as “safe.”

Mistake 2: Trusting only the paid tool Boldin PlannerPlus is excellent, but using only Boldin means your probability-of-success is based on 1,000 Monte Carlo scenarios from a single vendor. Running FIRECalc independently gives you a second method (historical sequences) from a different source.

Mistake 3: Using a robo-advisor as a planning tool Betterment and Personal Capital manage your portfolio. They are not retirement planning tools. A Betterment goal tracker is not Monte Carlo simulation.

Mistake 4: Never updating the model The two-tool stack is an annual practice, not a one-off. Update both tools with actual end-of-year numbers, new tax bracket information, and any changes to your plan.

The realism floor

A note on cost. The free layer (FIRECalc, cFIREsim, ProjectionLab free) takes you 80% of the way for $0. The paid layer ($109-$144/yr) is worth it once you’re within 10 years of retirement and the tax optimisation EV starts to matter. A one-off CFP consultation ($2,000-$3,000) is worth the “second pair of eyes” check but is not a substitute for the ongoing modelling these tools enable.

At above $300/yr for software: the EV calculation likely flips toward hiring a fee-only fiduciary for an annual planning session instead.

Sources: Boldin pricing, ProjectionLab pricing, FIRECalc methodology, IRS Publication 590-A (Roth conversion rules), IRS Publication 590-B (distribution rules). Affiliate disclosure: we earn commissions on Boldin signups. We earn $0 from FIRECalc, cFIREsim, ProjectionLab, and Maxifi.