Runway calculator vs spreadsheet: which one should you use?

A spreadsheet is the right tool for your first runway model, and it is still the right tool for a one-off static plan. It stops being the right tool at a specific point: when you need a range rather than a date, when an input changes and you have to re-derive the answer by hand, or when someone asks how confident you are in the number. This page is the honest comparison, including the rows where the spreadsheet wins.

The short answer

• Use a spreadsheet if the model is yours, the plan is static, and nobody outside the company has to rely on the output.
• Use a calculator when you want the answer now, with benchmarked starting assumptions and no chance of a broken formula.
• Outgrow both when the question stops being "what is my runway?" and becomes "how likely is it that I run out, and what moves the date?" A single number — from a sheet or from a calculator — cannot answer that.

Side by side

Time to a first answer: a spreadsheet takes whatever it takes to build the model, tens of minutes to hours; the free calculator takes seconds with no account; FounderConsole takes minutes once data is connected. What you get back: the sheet returns one cash-out date from the assumptions you typed; the calculator returns months of runway and a cash-out date from benchmarked inputs; FounderConsole returns a distribution — P10/P50/P90 bands, not one date. When an input changes: you edit cells and re-check the downstream formula; on the calculator you change the field and the answer updates; in FounderConsole the forecast updates from your connected data. Formula risk: real in a sheet, where a hardcoded cell or a broken range silently changes the date; none you can introduce in either tool. Where the assumptions come from: you, from memory or the last plan; benchmarked starting inputs you can override; your own connected financials. Sharing it: attach the file and hope the reader finds the cell that matters; send a link; share the scenario with reasoning you can show a board. Cost: free if you already have it; free with no account; every feature free during early access.

Where the spreadsheet wins

It is your model. Nobody else's tool decides what a line item means, how you treat a grant, or whether a hire lands in month 3 or month 4. A spreadsheet handles the irregular thing — a deferred payment, a one-off invoice, a seasonal month — without asking you to bend it into someone's form. It works offline, it is on your machine, and for a static plan you intend to look at once, building the model is not wasted effort: it is how you learn your own business. All of that stays true.

Where the spreadsheet breaks

• It gives you a date, and a date reads like a fact. The arithmetic is a straight line: $120,000 in the bank against $20,000 of net burn is six months. Real burn is not a straight line, so the honest output is a range of dates and a probability of running out — which a single-cell answer cannot express, however correct the cell is.
• It goes stale the day you build it. The model is correct as of the numbers you typed. The bank balance moves on Monday.
• The failure is silent. A hardcoded cell, a drag that stopped one row short, a formula copied across a column it should not have been — the sheet still returns a number, and the number still looks fine. Nothing warns you.
• It has no benchmark. A sheet will tell you what your assumptions imply. It will not tell you that the assumption itself is unusual for a company at your stage, because it has nothing to compare against.
• Reading it is a skill. Handing the file to a board member or a new hire transfers the model, not the understanding — including the part where you know which three cells actually matter.

The honest limit of a free calculator

A calculator fixes the formula risk and the staleness, and it gives you a benchmarked starting point instead of a blank grid. What it does not fix is the thing at the top of that list: it still returns one number, because you are still entering one set of assumptions. Moving the arithmetic out of your spreadsheet is worth doing — but if the only change is that a website does the multiplication, you have not yet answered the question your investor is asking.

What a range looks like instead

FounderConsole runs Monte Carlo simulations over your own connected numbers — thousands of runs produce P10/P50/P90 bands, so runway is a distribution rather than a date, and you can see which assumption moves it. The AI copilot answers strategic questions against the same numbers, with reasoning you can show a board. What FounderConsole ships is already set out on compare and features, and every feature is free during early access — see pricing.

Try the free side of the comparison first

No account required. Enter your cash, burn and revenue on the startup runway calculator and compare its answer with your sheet — if the two disagree, one of them has a broken assumption and it is worth knowing which. Paul Graham's default alive or default dead test asks the harder question behind the arithmetic, and the startup survival simulator estimates odds of survival rather than months. If you want industry-tuned starting inputs, start from the SaaS runway calculator. When you want the range rather than the date, get started free.