Burn Rate Calculator · Burn Rate & Cash Runway

Burn Rate Calculator

Calculate your monthly burn rate and cash runway from balance change over time

Currency
Balance & duration
$
$
months
How it works: Burn rate is calculated as (Initial balance − Final balance) ÷ Duration. Cash runway is how many more months the current final balance will last at that same burn rate.
Burn Rate & Cash Runway
Burn rate
— /mo
— cash runway — zero-cash date —
💚—
Burn rate
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Cash runway
— mo
Total cash used
—
Zero-cash date
—
Runway interpretation
Cash runwayCategoryWhat it means
Calculation breakdown
ItemValue
Understanding your results
Burn rate: How much cash you spend each month on average, calculated from the change between your initial and final balance over the given duration. If the final balance is higher than the initial balance, the "burn rate" is negative — meaning you're cash‑flow positive.
Cash runway: How many months your current (final) balance will last if you continue burning at the same rate. This assumes no revenue growth, no new funding, and no change in spending.
Zero‑cash date: The projected calendar month when your cash balance will reach zero, assuming today is your starting point.
Important: This calculator uses a simple linear model — it assumes a constant burn rate. Real startups often have irregular cash flows, seasonality, one‑time costs, and revenue growth. For a more detailed projection with growth rates, use the advanced Burn Rate Calculator. Always model conservatively.
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Faiq Ur Rahman

Founder & CEO, Toolraxy

Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.

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Introduction

Every founder eventually asks the same question: how many months do we have left? The answer comes from two data points, a start balance and an end balance, and a duration between them. Divide the difference by the months, and you have your burn rate. Divide your current cash by that burn rate, and you have your runway. This calculator does both steps, plus it projects the calendar month when your balance reaches zero. It was built for startup founders, finance leads, and small business owners who need a fast read on runway without opening a spreadsheet. It also handles the cash-flow positive case, where your balance grew instead of shrank. In that scenario the tool reports unlimited runway and flips the burn rate to a negative number.

 

How to Use the Burn Rate Calculator

  1. Choose your currency from the dropdown. All money fields adopt the matching symbol.

  2. Enter the balance at the start of the period. This is your opening cash.

  3. Enter the balance at the end of the period. This is your closing cash.

  4. Set the duration in months. Decimals work, so 3.5 is fine for a ten-and-a-half week window.

  5. Read the burn rate from the hero panel. It shows the monthly figure with your currency symbol.

  6. Check the cash runway tile for months remaining at the current burn rate.

  7. Look at the zero-cash date to see the projected month when your balance hits zero.

  8. Tap Calculate to force a fresh pass, or Reset to clear back to defaults.

 

How the Burn Rate Formula Works

Three formulas sit behind this tool. They run in sequence.

Formula: Total cash used = Initial balance − Final balance
Formula: Burn rate = Total cash used ÷ Duration in months
Formula: Cash runway = Final balance ÷ Burn rate

Total cash used is the raw difference between your opening and closing balances. Burn rate spreads that difference evenly across the period. Cash runway takes your current balance and divides it by the monthly burn to see how many more months it will last.

The tool handles one edge case that trips up a lot of spreadsheets. When your final balance is higher than your initial balance, the burn rate goes negative. That means you generated more cash than you spent. The calculator flags this as cash-flow positive and reports unlimited runway rather than a nonsensical negative number of months.

Inputs are clamped to sensible ranges. Balances cap at 10 billion in either direction. Duration runs from 0.01 months to 600 months. If the final balance is exactly zero, the category jumps straight to Critical regardless of the runway math, because there’s nothing left to burn.

 

Worked Example

A seed-stage company started January with $412,000 in the bank. By the end of June, the balance was $268,500. That’s six months of data.

Total cash used: $412,000 − $268,500 = $143,500.
Burn rate: $143,500 ÷ 6 = $23,916.67 per month.
Cash runway: $268,500 ÷ $23,916.67 = 11.2 months.

The tool would report a burn rate of about $23.9K per month, a runway of 11.2 months, and a zero-cash date roughly 11 months out. The category lands in Tight, since 11.2 falls between 6 and 12 months. The verdict banner would say to start investor conversations now and aim to close before runway drops below six months.

Now suppose the same company had ended June with $450,000 instead. Total cash used flips to negative: $412,000 − $450,000 = −$38,000. Burn rate becomes −$6,333 per month. The tool marks the company as cash-flow positive and shows unlimited runway. That’s a fundamentally different position, even though only one input changed.

Frequently Asked Questions

What is a burn rate?

Burn rate is the amount of cash a company spends each month. It’s calculated by dividing the change in cash balance over a period by the number of months in that period. A company that lost $120,000 over six months has a burn rate of $20,000 per month.

 

How do I calculate my cash runway?

Divide your current cash balance by your monthly burn rate. If you have $300,000 and burn $25,000 a month, you have 12 months of runway. The calculator does this automatically once you enter your balances and duration.

 

What is a good burn rate for a startup?

There’s no fixed number. What matters is the ratio of burn to cash. Investors want at least 12 months of runway after a raise and at least six months before starting the next one. Below six months of runway, you’re in a tight position.

 

Why is my burn rate negative?

A negative burn rate means your balance grew over the period. You brought in more cash than you spent, whether through revenue, fundraising, or a one-time inflow. The calculator treats this as cash-flow positive and reports unlimited runway.

 

How many months of runway should I have?

Eighteen to twenty-four months is healthy after a funding round. Twelve to eighteen is adequate but tight. Six to twelve means you should already be talking to investors. Below six, you’re raising from weakness. Below three, you’re in emergency territory.

 

What’s the difference between gross burn and net burn?

Gross burn is total cash spent. Net burn is cash spent minus cash received. This calculator measures net burn because it uses balance changes. If revenue came in during the period, it’s already reflected in the final balance.

 

How often should I recalculate burn rate?

Monthly at a minimum. Weekly if you’re within six months of running out. Burn rate drifts as you hire, change marketing spend, or adjust pricing. Running the numbers on a fixed cadence catches problems before they become urgent.

 

Can I use this calculator for personal finances?

Yes. It works for any situation where you have a starting balance, an ending balance, and a time period. Personal savings drawdown, household budgets, and side-project spending all fit the model. Just remember it measures net change, not gross spending.

 

What does the zero-cash date mean?

It’s the projected calendar month when your balance reaches zero, assuming the same burn rate continues. The calculator adds your runway in months to today’s date. It’s a rough estimate, not a forecast, because burn rates change over time.

 

Does burn rate include one-time costs?

The balance-based method does include them, because they show up in your ending balance. If you paid a large annual bill during the period, it inflates your burn rate for that window. That’s why six months of data usually gives a cleaner picture than one or two.

 

What happens if my final balance is zero?

The calculator flags the category as Critical and shows a runway of zero months. There’s no cash left to burn, so the runway math can’t produce a positive number. Immediate fundraising or restructuring is the only path forward at that point.

Disclaimer

This calculator uses a simple linear model based on your two balance figures and duration. It assumes a constant burn rate going forward, which real businesses rarely have. Seasonality, one-time costs, revenue growth, new hires, and funding events all change the picture. The zero-cash date is a projection, not a promise. Use this tool as a starting point for planning, not as a substitute for a cash flow forecast or advice from an accountant or CFO.

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