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Startup Runway Calculator

Months of cash left from MRR, growth, churn and burn, projected month by month, with the break-even point and what each lever adds.

Updated · By Niraj Kumar · 3 sources

Revenue and customers

$

ARPU $200 a month.

Retention

%
0%15%

Customers who cancel each month. 3% a month is 31% a year.

%
−2%5%

Upgrades and added seats less downgrades, from customers who stay. Gives NRR of 88%.

Margin and acquisition

%
0%100%

Revenue left after hosting, support, payment fees and third-party APIs.

$

Ads, tools and the pay of sales and marketing staff. CAC $1,800.

Cash

$
$

R&D, G&A, rent: everything outside cost of revenue and sales and marketing.

LTV settings

%

What future profit is worth today. 0 for an undiscounted LTV.

months

How long a customer's profit counts. 60 is common.

Cash runway20.7 monthsBurning $55,000 a month; break-even in month 59 comes too late
Customer lifetime value
$5,254
60 months, discounted 10%; simple LTV $4,800
CAC
$1,800
$18,000 ÷ 10 new customers
LTV:CAC
2.9:1
Below the 3:1 rule of thumb
CAC payback
12.5 months
12 to 18 months: typical
Net revenue retention
88%
Gross retention 69%; 31% of customers lost a year
Implied valuation
$945,000
3.1× ARR on 79% growth; Rule of 40: -141
What if you pulled one lever?Each row changes one input and leaves the rest as entered. Valuation moves in steps as growth, churn and NRR cross a band.
ChangeLTVLTV:CACPaybackValuationRunway
As entered$5,2542.9:112.5 months$945,00020.7 months
Cut monthly churn by 1 point+$1,571+0.87–+$270,000+2.1 mo
Add 0.5 points of monthly expansion+$675+0.38–+$135,000+0.8 mo
Acquire customers 10% cheaper–+0.32−1.3 mo–+1.3 mo
Raise gross margin by 5 points+$365+0.20−0.8 mo+$65,500+1.5 mo
One customer: gross profit less CACCAC not yet earned backProfit after CAC
-$2,000-$1,000$0$1,000Payback, month 13.3048121621

Expected profit from a new customer, allowing for the chance they churn and for expansion. Simple payback ignores churn: 12.5 months.

Cash in the bank, month by monthShort of cashCash in the bank
-$500,000$0$500,000$1,000,000Cash runs out, month 20.7061218243036

Burning $55,000 a month; break-even in month 59 comes too late. New customers join at today's ARPU; costs stay flat.

Against Early stage (under $1M ARR) benchmarksSeed-stage companies below $1M ARR, still finding repeatable acquisition. Checked October 11, 2026.
MetricYoursMedianStrongWhere you sit
Monthly churn3%3%1.5%Above median
Net revenue retention88%88%100%Above median
Gross margin72%70%80%Above median
CAC payback12.5 months15.0 months9.0 monthsAbove median

How is startup runway calculated?

Simple runway is cash ÷ monthly burn. A SaaS company's burn changes as MRR grows or churns, so this calculator projects cash month by month. The early-stage example burns $55,000 a month on $900,000: 20.7 months of runway.

ARPU = MRR ÷ customers; gross profit per customer g = ARPU × gross margin; annual churn = 1 − (1 − c)^12; NRR = ((1 − c) × (1 + e))^12; GRR = (1 − c)^12; simple LTV = g ÷ c; LTV = Σ g × q^t for t = 0 … H − 1, q = (1 − c)(1 + e) ÷ (1 + d)^(1/12); CAC = sales and marketing ÷ new customers; payback = CAC ÷ g; LTV:CAC = LTV ÷ CAC; cash(t+1) = cash(t) + MRR(t) × margin − sales and marketing − other costs; runway = months until cash < 0

This page uses the same method as the SaaS Unit Economics Calculator, which explains each term and assumption in full.

Worked example

A seed-stage SaaS on $25,000 MRR from 125 customers at $200 a month, adding 10 a month on $18,000 of sales and marketing, with 3% monthly churn, 2% monthly expansion, 72% gross margin, $55,000 of other monthly costs and $900,000 raised and unspent.

  1. 1Month 0: $25,000 × 72% gross profit − $18,000 sales and marketing − $55,000 other costs = -$55,000
  2. 2Simple runway: $900,000 ÷ $55,000 = 16.4 months
  3. 3Each month MRR keeps 97%, grows 2% and adds 10 customers, so burn shrinks
  4. 4Projected: cash runs out after 20.7 months

20.7 months of runway, break-even in month 59.

Frequently asked questions

What does default alive mean?

Paul Graham's term for a startup that reaches profitability on its current growth and costs before its cash runs out. Default dead means it needs to raise money or cut costs to survive. The calculator shows default alive when the projected cash never drops below zero over ten years.

How much runway should a startup have?

18 to 24 months after a funding round is the common target, because raising the next round takes 6 to 9 months and should start with a year left. Below 12 months, most founders cut burn or start fundraising immediately. Profitable or default-alive companies can run leaner.

Sources

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