# How to Calculate Your Startup Runway Without a CFO

> Runway is the number of months your company can keep paying its bills before the bank account hits zero. Most small founders know it only as a feeling, because the numbers sit in different places and nobody joins them on a calm day. You need three numbers and one division to work it out by hand, and this page shows you how.

- URL: https://www.agentskillpacks.com/products/ai-cfo-toolkit
- Product: AI CFO Toolkit
- Price: $19 one-time (USD), instant download, lifetime v1 updates
- Updated: 2026-10-21
- Seller: ToolGenX (https://www.agentskillpacks.com)

## Quick answer

To calculate startup runway, divide the cash you have in the bank by your monthly net burn. Net burn is what you spend in a month minus what you earn in that month. With $120,000 in cash and a net burn of $12,000, runway is 10 months. AI CFO Toolkit adds three Claude Code skills and two Python scripts that read your QuickBooks exports and print a monthly briefing, for a one-time $19.

## What AI CFO Toolkit is

AI CFO Toolkit is a founder toolkit of three Claude Code skills and two Python scripts: cfo-analyzer.py reads your QuickBooks CSV or XLSX exports and prints a CFO briefing on burn, runway and margins, and scenario-modeler.py projects base, bull and bear cases saved as JSON.

## Why do founders guess their runway?

Founders guess their runway because the numbers that make it up live in different places. Cash sits in the bank app. Spending sits in card statements and payroll. Revenue sits in Stripe or Gumroad. Nobody joins them on a calm day, so the answer comes out as "about eight months".

Guessing costs more than it looks:

- **You start raising too late.** A raise can take months. If you think you have eight months and you really have five, you start talking to investors when you are already in trouble.
- **You cut the wrong costs.** Without a clear burn number, you cut what feels big, not what moves the total.
- **Spreadsheets break quietly.** One cell that adds gross burn instead of net burn can add months that do not exist.

I learned the same lesson in my lighting business, not in software. A tender quote of mine lost its margin because required items were never priced as their own lines. Those items came to roughly a quarter to a third of the material cost per unit. My assistant's internet estimate for one material was 3.4 times what I actually pay. The sum was right. The inputs were wrong.

The sum itself is simple. The hard part is keeping clean inputs in one place, every month.

## How to calculate startup runway by hand, step by step

Startup runway is cash in the bank divided by monthly net burn. You need three numbers from the last three months: your cash today, your monthly spending, and your monthly revenue. Here is how to get each one, and then how to check your unit economics, which tell you whether growth will make runway longer or shorter.

### Part 1: runway

1. **Write down your cash today.** Use the real balance in your business bank account. Leave out money you expect but have not received yet.
2. **Add up your monthly spending.** This is your gross burn. Take each of the last three months. Add salaries, rent, software, ads, contractors and anything else that left the account. Then take the average.
3. **Add up your monthly revenue.** Use cash that actually arrived, not invoices you sent. Average the same three months.
4. **Work out net burn.** Net burn = gross burn minus revenue. This is how much cash you lose each month. The investor firm a16z describes it the same way in its guide to [16 startup metrics](https://a16z.com/16-startup-metrics/).
5. **Divide.** Runway in months = cash divided by net burn. This is the same formula Canada's business bank BDC gives in its [cash runway definition](https://www.bdc.ca/en/articles-tools/entrepreneur-toolkit/templates-business-guides/glossary/cash-runway).

**A worked example (made-up numbers, for learning only):** you have $120,000 in the bank. You spend $18,000 a month and earn $6,000 a month. Net burn is $18,000 minus $6,000, which is $12,000. Runway is $120,000 divided by $12,000, which is 10 months.

6. **Do a growth check.** Runway assumes nothing changes. Paul Graham's essay [Default Alive or Default Dead](https://paulgraham.com/aord.html) asks a sharper question: if spending stays flat and revenue keeps growing at its recent rate, do you reach profit before the cash runs out? If yes, you are "default alive". If no, you need to raise, cut, or grow faster.

### Part 2: unit economics

Unit economics means the money you make and spend for one customer. Three numbers matter most.

7. **Find your CAC.** CAC means customer acquisition cost: what you spend to win one new customer. Add up sales and marketing spend for a month and divide by the new customers you won that month. Count everything, including discounts and referral fees.
8. **Find your monthly gross profit per customer.** Take what one customer pays per month and subtract what it costs you to serve them, such as hosting or payment fees.
9. **Find your payback period.** Payback = CAC divided by monthly gross profit per customer. It tells you how many months it takes to earn back what you spent to get that customer.
10. **Find your LTV.** LTV means lifetime value: what one customer is worth to you over the whole time they stay. A simple version is monthly gross profit times the average number of months a customer stays. You can estimate that as 1 divided by your monthly cancel rate.

**A worked example (made-up numbers again):** you spend $3,000 on ads and win 60 customers, so CAC is $50. Each customer pays $20 a month and costs you $4 to serve, so gross profit is $16. Payback is $50 divided by $16, a little over 3 months. If 5% of customers cancel each month, they stay about 20 months on average, so LTV is $16 times 20, which is $320.

### Part 3: put the two together

11. **Ask what growth does to runway.** If payback is short, new customers pay for themselves soon, and growth can stretch runway. If payback is longer than your runway, every new customer makes the cash problem worse for a while.
12. **Update it monthly.** Put the date next to every number. Runway from three months ago is a history lesson, not a plan.

Pricing feeds all of these numbers, but it is a separate job. I wrote up how to test a price with [the Van Westendorp survey](/blog/pricing-a-digital-product-with-van-westendorp), and the free [digital product pricing calculator](/digital-product-pricing-calculator) does the margin maths for you. In my own quotes I raised the price floor on large jobs from 1.5 times cost to 2 times, so the first payment covers every cost of the job.

## The faster way: a CFO briefing from your QuickBooks exports

The faster way is to let a script read the reports your books already produce, so you stop retyping numbers. AI CFO Toolkit does that for founders on QuickBooks. You export your P&L and any other reports into one folder, and a Python script prints a briefing on revenue, margins, people costs, tools and burn.

To be plain: there is no spreadsheet in the download. It is three [Claude Code skills](/blog/best-claude-code-skills-for-indie-developers) and two Python scripts. If you want a sheet you type into, the by-hand steps above build one.

### How to use it, step by step

1. **Buy and download.** Gumroad sends the files right after payment.
2. **Install the three skills in Claude Code.** Copy `skills/pricing-strategy`, `skills/analytics-tracking` and `systems/finance-ops` into `~/.claude/skills`.
3. **Install the script packages.** Inside the finance-ops folder, run `pip install -r requirements.txt`. It needs pandas and openpyxl.
4. **Export your reports from QuickBooks** as CSV or XLSX into one folder. A P&L alone is enough to start. A cash flow report adds monthly burn.
5. **Run the briefing.** Type `/finance-ops briefing` in Claude Code, or run `python scripts/cfo-analyzer.py --input` with your folder. The script saves each month to a history folder, so next month it can compare.
6. **Model scenarios.** Run `/finance-ops scenario` to compare a base case, a bull case where growth targets land, and a bear case where you lose a share of revenue.
7. **Check unit economics.** Run `/analytics-tracking unit-economics` with your revenue per customer, churn and CAC.

One gap you should know about: the finance-ops skill file starts by calling two small telemetry scripts that are not in the download. Those calls fail quietly and the rest still runs.

### What the output looks like

The briefing is plain text in your terminal: revenue first, then profitability, people costs, tools, operating expenses and debt. Each metric gets a green, yellow or red status against a threshold in an editable guide. The default marks gross margin above 60% as healthy and below 45% as needing action. Cash runway above 3 months is healthy, and under 1 month needs action. If a prior month is saved, each line also shows the change month over month.

### How much time it saves

I have not timed it on my own books yet, so I will not give you a number. The saving that matters is the second month. You export the same reports, run the same command, and the briefing shows what changed, instead of you rebuilding a sheet you no longer trust.

For scale, Pilot, a startup accounting firm, put fractional CFO fees at $3,000 to $12,000 a month in its [August 2025 cost guide](https://pilot.com/blog/fractional-cfo-cost-guide), with light early-stage help near the low end. This kit does not replace that judgement. It gets your numbers ready before you pay for it.

## By hand vs a generic AI prompt vs AI CFO Toolkit

The maths is the same in all three columns. Runway is still cash divided by net burn. What changes is where the numbers come from, how easy it is to break a formula, and whether you can repeat the check next month without rebuilding it.

| | By hand | Generic AI prompt | AI CFO Toolkit |
| --- | --- | --- | --- |
| Getting to a first number | Three numbers and one division, once you have gathered them | Quick to get a formula, slow to check it against your real bank data | One script run on a folder of QuickBooks exports; I have not published a timing |
| Formula errors | Easy to make, hard to spot at midnight | The model can mix up gross and net burn if you do not say which | The script does the sums; you check that its expense categories match your accounts |
| CAC, LTV and payback | You build each sum yourself | Explained well, but you still build the sheet | A unit economics skill that asks for revenue per customer, churn and CAC |
| Best, base and worst case | Copy the sheet three times and hope they stay in sync | Gives you a plan, not a working model | A script that projects base, bull and bear cases 12 months ahead |
| Ready to show someone | You write the summary from scratch | Drafts a summary from numbers you paste in | A plain-English briefing with a green, yellow or red status per metric |
| Cost | Free, plus your evenings | Your existing AI plan | $19 once, plus Python and your Claude plan |

## What is inside AI CFO Toolkit

AI CFO Toolkit is three Claude Code skills and two Python scripts for founders. A script reads your QuickBooks exports and prints a briefing on revenue, margins, costs and burn. The skills add scenarios, pricing and a unit economics check.

- finance-ops: a Claude Code skill plus cfo-analyzer.py, which reads QuickBooks exports (CSV or XLSX) and prints a CFO briefing
- scenario-modeler.py: base, bull and bear projections 12 months ahead, printed and saved as JSON
- A cost estimate mode for checking a new tool, hire or build before you commit to it
- pricing-strategy: value metrics, a three-tier structure and the four Van Westendorp questions
- analytics-tracking: a unit economics check for LTV, LTV to CAC, payback and net revenue retention
- Benchmark thresholds you can edit, such as cash runway above 3 months marked healthy

### What you do not get

- No spreadsheet or Google Sheets template. The output is a text briefing and JSON files.
- No bookkeeping. It reads exports from QuickBooks; it does not record transactions.
- No financial advice. The briefing shows your numbers, and the decisions stay with you.

## Who AI CFO Toolkit is for, and who should skip it

This toolkit fits founders who keep their books in QuickBooks, make money decisions alone and can run a Python script. It does not fit a company that already has a finance team, or someone who wants a ready spreadsheet.

- For you if: You answered "how much runway is left" with a guess and a smile.
- For you if: You have an investor call coming and your numbers live in four different places.
- For you if: You know your revenue but not your CAC, LTV or payback period.
- For you if: You want to see what happens to cash if a big client leaves, before it happens.
- Skip it if: You have a finance team or a fractional CFO you trust. They already build these models.
- Skip it if: You want a spreadsheet to type into. This kit is scripts and skills, not a sheet.
- Skip it if: Your books are not in QuickBooks and you cannot export a P&L as CSV or XLSX.

## FAQ

### How do you calculate startup runway?

Divide the cash in your bank account by your monthly net burn. Net burn is your monthly spending minus your monthly revenue. If you hold $90,000 and lose $15,000 a month, your runway is 6 months. Use an average of the last three months so one odd month does not skew it.

### What is the difference between gross burn and net burn?

Gross burn is everything you spend in a month. Net burn is gross burn minus the money that came in. Runway uses net burn, because revenue slows the loss of cash. Before you have any revenue, the two numbers are the same.

### Do I need accounting knowledge to use AI CFO Toolkit?

You need to know where your books live and how to export a report. The briefing is written in plain English, and each metric gets a green, yellow or red status against a threshold you can change. You also need to run a Python script from a terminal.

### Does it work with ChatGPT?

The Python scripts run on your own computer with no AI tool at all. The three skills are written for Claude Code, where you type commands such as /finance-ops briefing. You can paste the briefing into ChatGPT to help write an investor update, but the numbers come from the script.

### Is it a one-time payment?

Yes, AI CFO Toolkit costs $19 once. There is no subscription. You get the files as a download from Gumroad right after payment.

### What does it ship as?

It ships as a zip with three skill folders and two Python scripts. The scripts need Python with pandas and openpyxl, listed in a requirements file. There is no spreadsheet file in the download. The output is a text briefing in your terminal plus JSON you can keep.

### How is this different from hiring a fractional CFO?

A fractional CFO is a part-time finance expert who brings judgement and experience. Pilot, a startup accounting firm, put fractional CFO fees at $3,000 to $12,000 a month in August 2025. The toolkit gives you the numbers a CFO would look at first, but not the advice. If you can afford both, use both.

### How much runway should a startup have?

Venture firm CRV suggests 18 to 24 months in its runway guide. It says to start raising with 12 to 18 months left, since a raise takes three to six months.