How to build a healthy budget for your startup

TL;DR

• Separate fixed, variable, and one-time expenses; reserve budget for nice-to-haves last, and consider building a cushion for unexpected costs.
• Balance cash conservation with growth spending by prioritizing essential costs first, since early-stage startups often have more control over expenses than income.
• Align budget with company goals, growth strategy, and risk tolerance; get department buy-in and agree in advance on revenue benchmarks that trigger spending increases.
• Use scenario planning to shift spending quickly across different revenue outcomes, keeping flexibility as a core feature of your budget.
• Review budget monthly against actuals, but only revise it when a meaningful trend or major shift emerges.

A startup’s budget can feel like a catch-22. If you spend too much money before revenue comes in, you’ll quickly find yourself in a hole you might not be able to climb out of. If you spend too little, your growth will be slow — all while you’re still incurring expenses.

Even if you’ve received a VC investment to help bring your product to market, you still have to create a realistic budget. With effective budgeting, you can manage your cash flow and invest in the right areas of your business (such as additional employees or new equipment). We’ve rounded up some things to consider as you establish your budget and modify it as you grow.

Your startup’s budget may seem full of unknowns. It often is: you’re spending money in advance of revenue to get your business off the ground.

Building a sustainable business means planning how much you’ll spend before you can realistically expect more revenue. Here's what to keep in mind as you map out your budget:

Your expenses

In the early days, you’ll have more control over your expenses than your income. But what should you spend on when your revenue is unpredictable or minimal?

It helps to break down your expenses into two categories: essential and nice-to-have. Essential expenses are required to keep the lights on: costs related to your employees, your website, and any cloud storage or hosting, or any costs associated with selling or delivering your product. Nice-to-haves might be things like tools that make your employees’ jobs easier, a generous marketing budget for a big brand awareness campaign, or fees associated with attending conferences or sponsoring industry events.

You can further categorize your expenses by fixed costs versus variable costs versus one-time expenses. Your essential, fixed costs should be the most predictable and first in your budget. Then you’ll consider costs that are essential, but might vary every month. You may have one-time costs (like computer equipment) that are necessary upfront but won’t happen every month.

The last part of your budget will be dedicated to your “nice-to-haves” — and that’s where you’ll need to consider how much you want to spend, knowing that the expenses will burn cash. You’ll also want to think about a cushion in your budget for unexpected expenses, or set up a savings account as an emergency fund. As a general rule, aim to keep enough cash on hand to cover at least 3 to 6 months of essential operating expenses. Earlier-stage startups with less predictable revenue may want a larger cushion, while later-stage companies with more predictable revenue may be able to plan around a more precise runway target.

As you map these categories, be specific about the line items in each bucket. Essential expenses might include payroll, contractor support, cloud hosting, payment processing, accounting, legal, insurance, security tools, and customer support software. Nice-to-haves might include conference sponsorships, premium software, brand campaigns, team offsites, or experimental marketing channels. It’s also worth watching for hidden costs that can grow unnoticed, like cloud egress fees, usage-based software pricing, chargebacks, returns, shipping materials, or support tools that become more expensive as your customer base grows. 

Example startup budget

Here’s how this might look for an early-stage SaaS startup with $400,000 in cash and $20,000 in monthly revenue.

In this example, the startup has enough runway to keep operating for nearly a year at the current burn rate. But the budget also shows where decisions could be made if revenue comes in below plan. Paid marketing tests and conference travel could be reduced first, for example, while essential costs like payroll, infrastructure, accounting, and hosting would be protected.

How to calculate monthly burn and runway

Once you’ve mapped your expenses, calculate two basic numbers: monthly burn and runway.

Monthly burn = cash out − cash in

For example, if your startup spends $54,700 in a month and brings in $20,000 in revenue, your monthly burn is $34,700.

Runway = cash on hand ÷ monthly burn

Using the example above, a startup with $400,000 in cash and a monthly burn of $34,700 has about 11.5 months of runway.

These numbers won’t tell you everything about the health of your business, but they give you a practical baseline for decision-making. If your runway is shorter than expected, you may need to reduce variable spending, delay nice-to-have expenses, revisit hiring plans, or accelerate revenue-generating work.

Department buy-in

Even if your startup is small and you have teams of one, you should get buy-in for your budget. For example, your head of marketing should understand the amount of money dedicated to advertising or content. You should collectively agree on the salaries and number of employees for different roles like engineers or customer services.

Your team should understand why budget decisions are made: why you’re opting to spend money on one cost versus another. Your budget may go through several iterations before you come to a consensus.

Your leadership team and/or department heads can also collectively agree to increase the budget if certain targets are met. This might include adding a new employee when revenue hits a certain point or using additional cash for a larger investment. By deciding on revenue benchmarks, everyone knows when more money will be available in the budget.

To keep budget conversations productive, turn this into a monthly variance review. The goal is to compare your budget to actual results, identify what changed, and decide whether anything needs to be cut, deferred, or reallocated. 

You can also set decision thresholds so small differences don’t slow the team down. For example, department owners might manage budget variances under 5-10% without escalation, while anything above 10%, or any unplanned expense that affects runway, should be escalated.

A short monthly budget review agenda might include:

• Review cash on hand, monthly burn, and runway
• Compare budgeted revenue and expenses to actuals
• Identify the largest variances and their causes
• Decide what to cut, defer, or approve
• Confirm owners and follow-up dates

This keeps budget conversations focused on decisions rather than debate.

Scenario planning

As you consider different revenue targets, such as reaching a certain MRR, you’ll also want to plan for various scenarios. This is especially true if your revenue is less predictable, like ecommerce revenue, or if you have seasonal periods with less control over your sales volume.

With scenario planning, you’ll create several “what if” scenarios before you need them. Your essential versus nice-to-have expenses should factor into each scenario, along with clear actions you’ll take if certain triggers are hit.

If you have multiple scenarios planned out, you can adapt more quickly to changes in revenue. You won’t need to spend time plotting out a new budget; instead, you can shift to the actions you already agreed on.

A typical year-long budget should still reflect your long-term goals. The spending for a product-led company will look very different than that of a sales-led organization, and so on. Two startups could be placed side-by-side, with similar funding, and allocate their spending much differently.

You have to start with your vision and how you plan to get there. The numbers should align around that vision. A lot of it will depend on your tolerance for risk and how aggressive you want to be with growth.

A simple way to make this tangible is to connect each major company goal to the budget lines that support it and the metrics you’ll use to evaluate progress. 

This helps your budget become more than a list of expenses. It becomes a way to show how each dollar supports a specific business outcome. 

If your goal is to stretch out your cash as long as possible, that will dictate your budget. If you want to make a splash in the marketplace, you may spend a lot in the early months. Your budget, your goals, and your cash on hand: they’re all intertwined.

Your budget should also reflect your company’s stage.

Pre-revenue: Spending usually centers on product development, legal setup, core tools, and founder or contractor support. The priority is preserving runway long enough to validate the product and reach early customers.

Post-PMF: Once you have clearer evidence of product-market fit, the budget often shifts toward repeatable growth. This may include customer support, onboarding, paid acquisition tests, sales tools, and finance operations.

Scaling: As the company grows, people costs, compliance, infrastructure, and management systems often become a larger share of the budget. At this stage, the goal is less about proving demand and more about managing efficiency, predictability, and operating leverage.

Creating your budget is only half of the process. The other half is comparing your actual income and expenses to your budget. Do a monthly comparison between your budget and your financials.

In that review, look at cash on hand, monthly burn, runway, revenue, and the largest expense variances. Then ask:

• Are we ahead of plan, behind plan, or roughly on track?
• Are the biggest variances one-time issues or emerging trends?
• Do we need to cut, defer, or reallocate spending?
• Are any changes needed to protect runway or support a major goal?

Even though you’re doing the comparison, you don’t want to adjust your budget unless something changes drastically. Because of the volatility of startups, one bad month may not be a reason to shift your budget. You’ll only want to change your budget if you notice a trend or consistently miss your targets.

The healthiest budget you can create is one that has flexibility. As you grow and have more predictable revenue, you can make more long-term budget decisions. But the beauty of being a startup is that you can react to change quickly — and that includes managing your budget.

Want a clearer view of the trends behind your budget? Mercury Insights gives startups real-time visibility into where money is coming from, where it’s going, and how cash flow patterns are changing over time, all within your Mercury account. Explore Mercury Insights.