How Bootstrapped Runway Calculator works

1. Scope

Projects personal runway for a solo founder drawing on savings plus side income while MRR compounds. It does not model taxes precisely, investment returns on idle cash, or category-level cost-of-living inflation.

2. Inputs and outputs

Engine source: src/lib/bootstrapped-runway-calculator/engine.ts

3. Formula / scoring logic

for month m = 1..horizon:
  mrr_m      = starting_mrr * (1 + growth) ^ m
  shortfall  = max(0, monthly_expenses - side_income - mrr_m)
  savings_m  = savings_{m-1} - shortfall
stop when mrr_m + side_income >= monthly_expenses (ramen-profitable)
stop when mrr_m >= monthly_expenses (fully profitable)
stop when savings_m <= 0 (cash-out)

4. Assumptions

• MRR growth compounds monthly at a constant rate — no seasonality.
• Side income is steady. Irregular income should be averaged before entry.
• Taxes and one-offs (insurance, quarterly estimated tax) are captured inside monthlyExpenses or ignored.

5. Data sources

• US BLS Consumer Expenditure Survey (for users anchoring monthlyExpenses to benchmarks) as of 2024

6. Known limitations

• Constant-growth MRR is optimistic past month 12. For longer horizons, consider a staged growth assumption (ramp → plateau) outside the tool.
• No tax engine: rough rule of thumb is to pre-tax expenses by 20–30% before entry, or use the Freelance Tax Estimator for the side-income line.
• Cash-out logic assumes savings are liquid. Home equity, retirement accounts, and locked instruments are not runway.

7. Reproducibility

8. Change log

• 2026-04-24 methodology page first published.

Worked example

Run live against the same engine this site ships (/engines/bootstrapped-runway-calculator.js). The inputs and outputs below are recomputed on every build and independently re-verified in CI — they are never hand-authored.

Frequently asked questions

What does the Bootstrapped Runway Calculator calculate?

Projects personal runway for a solo founder drawing on savings plus side income while MRR compounds. It does not model taxes precisely, investment returns on idle cash, or category-level cost-of-living inflation.

What inputs does the Bootstrapped Runway Calculator need?

It takes 5 inputs: savings, monthlyExpenses, sideIncome (default 0), startingMrr (default 0), mrrGrowthRate (default 0). Outputs returned: monthsToRamen, monthsToFullyProfitable, runwayMonths, monthlyTrajectory.

What formula does the Bootstrapped Runway Calculator use?

The exact computation is: for month m = 1..horizon:; mrr_m = starting_mrr * (1 + growth) ^ m; shortfall = max(0, monthly_expenses - side_income - mrr_m); savings_m = savings_{m-1} - shortfall; stop when mrr_m + side_income >= monthly_expenses (ramen-profitable); stop when mrr_m >= monthly_expenses (fully profitable); stop when savings_m <= 0 (cash-out)

Can I verify the Bootstrapped Runway Calculator with a worked example?

Yes. With savings = 20000, monthlyExpenses = 3500, sideIncome = 1500, startingMrr = 200, mrrGrowthRate = 10%. the tool returns Ramen-profitable at ~month 13 (MRR + side ≥ expenses); runway to cash-out ~month 14 at baseline.

Where does the Bootstrapped Runway Calculator get its benchmark data?

Reference data is sourced from: US BLS Consumer Expenditure Survey (for users anchoring monthlyExpenses to benchmarks) (as of 2024).

What can the Bootstrapped Runway Calculator not tell me?

Known limitations: Constant-growth MRR is optimistic past month 12. For longer horizons, consider a staged growth assumption (ramp → plateau) outside the tool. No tax engine: rough rule of thumb is to pre-tax expenses by 20–30% before entry, or use the Freelance Tax Estimator for the side-income line. Cash-out logic assumes savings are liquid. Home equity, retirement accounts, and locked instruments are not runway.