Four inputs are enough to know whether an idea can work. The output leads with profit rather than revenue, because a business grossing $12,500 a month and spending $12,000 is not the company the revenue figure suggests.
Can My SaaS Idea Make Money?
Four numbers in. Revenue, costs, profit, margin and break-even out.
$/mo
$/mo
Hosting, APIs, support — scales with customers
$/mo
Salaries, tools, marketing
Ignores acquisition cost and churn, both of which decide whether you ever reach the customer count you entered.
Monthly profit$6,50052.0% net margin — $78,000 a year
- Revenue
- $12,500$150,000 ARR
- Cost to serve
- $2,000
- Gross profit
- $10,50084%
- Fixed expenses
- $4,000
- Profit
- $6,500
Each customer contributes $42 above the cost of serving them, so you break even at 96 customers.
The number that decides everything
Contribution margin is price minus the cost of serving one customer. At $50 with $8 of hosting, support and API cost, each customer contributes $42 toward fixed expenses.
contribution = price - cost to serve
= $50 - $8 = $42
break-even = fixed expenses / contribution
= $4,000 / $42 = 96 customersNote it is not $4,000 ÷ $50 = 80. Using price instead of contribution understates break-even, and the error grows as cost to serve rises.
Three ways an idea fails here
| Result | What it means | What to change |
|---|---|---|
| Negative contribution | Each customer loses money | Price or cost to serve — volume cannot help |
| Positive contribution, negative profit | Model works, not enough customers yet | Reach break-even, or cut fixed costs |
| Thin margin at your customer ceiling | Works only at scale you may not reach | Raise price or narrow the audience |
The first is fatal and the only one that cannot be solved by growing. The other two are timing and ambition problems.
Sanity-check your inputs
- Cost to serve should include hosting, per-customer APIs, support time and payment fees. Payment fees alone are 3–4% of a typical plan.
- Fixed expenses should include your own salary if you intend to take one, or the number is not a real profit figure.
- Customer count is the input most likely to be optimistic. Halve it and see whether the answer survives.
If the model only works at your most optimistic customer number, it does not work yet.
GOOD QUESTIONS
Frequently asked
What should I include in cost to serve?+
Everything that rises when you add one customer: hosting and infrastructure, per-use third-party APIs, support time, and payment processing fees. Payment fees alone are typically 3–4% of a monthly plan and are the line most often forgotten.
Should I include my own salary in fixed expenses?+
If you intend to take one, yes — otherwise the profit figure is not really profit, it is just what is left before paying yourself. The founder salary calculator works the requirement out properly.
Why is break-even higher than fixed expenses divided by price?+
Because each customer costs something to serve, so only the contribution — price minus cost to serve — is available to cover fixed expenses. With a $50 price and $8 cost to serve, you need 96 customers to cover $4,000, not 80.
What is a good net margin for SaaS?+
Profitable bootstrapped SaaS commonly runs 20–40% net. Venture-backed companies frequently run negative by choice, spending gross profit on growth. Neither is right or wrong — but the number should be a decision rather than an accident.