Key takeaways
- Profit is an opinion; cash is a fact. Most businesses fail from running out of cash, not from being unprofitable.
- The tool projects a running monthly balance from simple inflow/outflow items.
- It detects your runway — the first month cash goes negative — automatically.
- Handles one-off, monthly, and quarterly items, with start/end months.
- Free, open-source (MIT), downloadable from GitHub.
Excel Cash-Flow Forecast is a free, open-source tool that projects your month-by-month cash balance and tells you exactly when — if ever — you run out of money. List your recurring and one-off inflows and outflows, set a starting balance, and it returns a running balance for every month plus a clear runway warning. It's the answer to the single most important question in small- business finance: "how long can we last?"
Why a cash-flow forecast beats a P&L
A profit-and-loss statement can look healthy while your bank account quietly drains. Revenue is booked before customers pay; big bills land all at once; a tax payment or an annual software renewal blows a hole in a "profitable" month. That timing is invisible on a P&L but fatal in reality — and it's exactly what a cash-flow forecast makes visible.
The metric that matters is your runway: the number of months until you run out of cash at the current burn. Knowing it turns a vague worry into a deadline you can act on — raise money, cut costs, or pull in revenue before the wall, not after.
What the tool does
| Feature | What you get |
|---|---|
| Running balance | Your cash position at the end of every month in the horizon. |
| Recurring items | Mark items as once, monthly, or quarterly, with optional start/end months. |
| Runway detection | The first month the balance goes negative — flagged automatically. |
| Lowest point | Your tightest month, so you know the danger zone even if you never go negative. |
How to download & set up (about 2 minutes)
Free and open-source on GitHub. You'll need Python 3.9+.
- Download the code (or Code → Download ZIP on GitHub):
git clone https://github.com/Synth88Labs/excel-cashflow-forecast.git cd excel-cashflow-forecast - Install the two dependencies (pandas & openpyxl):
pip install -r requirements.txt - List your cash items in a CSV — name, type (inflow/outflow), amount, start month,
frequency — then run:
python cashflow.py cash_items.csv --start-balance 20000 --months 12
⬇️ Get Excel Cash-Flow Forecast on GitHub (free)
monthly
outflow starting in month 4, or a funding round as a once inflow in month 6, and watch how
your runway changes. It's a what-if planner, not just a report.
A worked example
Projecting a starting balance of $20,000 across a year of recurring items:
python cashflow.py sample_data/cash_items.csv --start-balance 20000 --months 12
Excel Cash-Flow Forecast
Start balance: 20,000
Month 1: 18,300 Month 2: 15,100 Month 3: 9,400
Month 4: 3,200 Month 5: -2,700 ...
Lowest balance: -8,900 (month 7)
RUNWAY: cash goes negative in month 5The business looks fine for a quarter — then the running balance reveals it crosses zero in month 5, with the tightest point in month 7. That's four months of warning to raise, cut, or accelerate. Without the forecast, you'd discover it the day a payment bounces.
Who this is for
- Startups & founders — track runway between funding rounds.
- Small businesses — anticipate seasonal cash crunches before they bite.
- Freelancers & agencies — plan around lumpy client payments.
- Finance teams — a fast, versionable alternative to a fragile spreadsheet.
Frequently asked questions
Is Excel Cash-Flow Forecast free?
Yes — open-source under the MIT license, free for personal and commercial use.
What exactly is "runway"?
The number of months until your cash balance hits zero at the current rate. This tool flags the first negative month for you automatically.
Can it handle irregular items like quarterly taxes?
Yes. Each item can be once, monthly, or quarterly, with optional
start and end months — so a quarterly tax or an annual renewal lands in the right months.
What input does it need?
A simple CSV of items (name, type, amount, start month, frequency) and a starting balance. The repo includes a sample you can copy.
Does it forecast revenue for me?
No — you supply expected inflows and outflows; it does the balance math and runway detection. Pair it with Excel Forecast Studio if you want statistical revenue projections to feed in.
Can I export the result?
Yes — use -o to write the full monthly projection to a CSV you can chart in Excel.
Summary
Running out of cash rarely happens suddenly — it happens predictably, if you're looking. Excel Cash-Flow Forecast projects your monthly balance and names the month you'd go negative, free and open-source. Download it, list your inflows and outflows, and turn "are we going to be okay?" into a number you can plan around.