Home › Business & Marketing › Burn Rate and Runway Calculator

Burn Rate and Runway Calculator

Computes gross burn, net burn (expenses minus revenue) and the runway in months from a cash balance, and the projected date the cash runs out when a start date is given.

When to use

You are a startup or project with a fixed cash pile and want to know how long it lasts at current spending and revenue.

Do not use when: Revenue or costs change month to month (model each month separately) or you need a loan payoff or savings timeline (use debt-payoff or savings-goal).

Formula

net_burn = monthly_expenses − monthly_revenue; runway_months = cash_balance / net_burn; zero_cash_date = start_date + runway_months × 30.4375 days

Assumes constant monthly expenses and revenue; the 'default alive' test would instead grow revenue at its current rate. Common guidance is to start fundraising with at least 6–9 months of runway left.

Inputs

Parameter	Type	Required	Description
`cash_balance`	number	yes	Cash and equivalents available today. Range: ≥ 0, ≤ 10000000000000
`monthly_expenses`	number	yes	Total cash spent per month (salaries, rent, tools, marketing). Range: ≥ 0, ≤ 1000000000000
`monthly_revenue`	number	default 0	Cash received per month; 0 for a pre-revenue company. Range: ≥ 0, ≤ 1000000000000
`start_date`	date	no	Optional date of the cash balance (YYYY-MM-DD); enables the zero-cash date.

Outputs

Output	Type	Unit	Description
`gross_burn_per_month`	number		monthly_expenses.
`net_burn_per_month`	number		monthly_expenses − monthly_revenue (negative means cash-flow positive).
`runway_months`	number	months	cash_balance / net burn (only when net burn > 0).
`months_of_expenses_covered`	number	months	cash_balance / gross burn, i.e. runway if all revenue stopped (only when expenses > 0).
`zero_cash_date`	date		start_date + runway_months × 365.25/12 days (only when start_date given and net burn > 0).
`runway_status`	string		Plain-language summary.

Example

500,000 cash, 60,000 expenses, 20,000 revenue from 2026-01-01: {"cash_balance":500000,"monthly_expenses":60000,"monthly_revenue":20000,"start_date":"2026-01-01"} → {"gross_burn_per_month":60000,"net_burn_per_month":40000,"runway_months":12.5,"months_of_expenses_covered":8.33,"zero_cash_date":"2027-01-16"}

120,000 cash, 25,000 expenses, no revenue: {"cash_balance":120000,"monthly_expenses":25000} → {"net_burn_per_month":25000,"runway_months":4.8,"months_of_expenses_covered":4.8}

GET https://tttkmbb.com/api/v1/calculate/burn-rate-runway?cash_balance=500000&monthly_expenses=60000&monthly_revenue=20000&start_date=2026-01-01

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/burn-rate-runway (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/burn-rate-runway · Markdown: https://tttkmbb.com/business/burn-rate-runway.md · JSON definition: https://tttkmbb.com/business/burn-rate-runway.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="burn-rate-runway"
OpenAPI operationId: calculate_burn_rate_runway
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Burn rate (reference)
Investopedia – Burn Rate: What It Means and How to Calculate It (reference)
Andreessen Horowitz – 16 Startup Metrics (reference)

FAQ

Gross or net burn?

Gross burn is total spending; net burn subtracts revenue and determines runway. Investors usually quote net burn.

What if revenue exceeds expenses?

Net burn is negative, the company is cash-flow positive and runway is unlimited; the calculator reports that status instead of a number.

Related calculators

MRR Growth Calculator — Project the revenue side over the same months.
Add or Subtract Days Calculator — Date arithmetic for a specific number of days.
Break-Even Calculator — Sales volume at which burn reaches zero.