What the SaaS metrics calculator measures
Most SaaS dashboards show one number at a time. This calculator takes six monthly inputs and turns them into the seven metrics that describe the health of a subscription business: MRR, ARR, customer churn, LTV, CAC, LTV:CAC and CAC payback. It then rates the four that have widely used benchmarks and names the weakest one, so you know where to look first.
Use numbers for a single month. Mixing a quarterly marketing budget with monthly churn is the most common reason these metrics come out wrong.
How each metric is calculated (worked example)
The sample numbers describe a small B2B product:
- Customers at the start of the month: 300
- New customers: 20
- Churned customers: 8
- ARPA (average revenue per account): $250 a month
- Gross margin: 80%
- Sales and marketing spend: $36,000
From those inputs:
- MRR = customers at the end × ARPA = 312 × $250 = $78,000, up 4.0% on the $75,000 you started with
- ARR = MRR × 12 = $936,000
- Customer churn = 8 ÷ 300 = 2.67% a month, or 27.7% a year once compounded
- LTV = $250 × 80% ÷ 2.67% = $7,500 of gross profit per customer
- CAC = $36,000 ÷ 20 = $1,800
- LTV:CAC = $7,500 ÷ $1,800 = 4.2:1
- CAC payback = $1,800 ÷ ($250 × 80%) = 9 months
How the metrics connect
These numbers are not independent. LTV:CAC multiplied by payback months always equals the average customer lifetime in months. In the example, 4.17 × 9 = 37.5 months, which is 1 ÷ 2.67%. That is why churn shows up everywhere: it sets LTV, and LTV sets the ratio.
It also explains why one metric can look fine while another does not. A short payback with low LTV:CAC means customers pay you back quickly and then leave. A strong ratio with slow payback means customers stay for years but tie up cash for a long time before they turn a profit.
What good SaaS metrics look like
Benchmarks depend on who you sell to and how you price, so treat these as typical ranges, not targets:
- Monthly customer churn: under 1% is excellent, 1–3% is common for products sold to small and mid-sized businesses, above 5% needs attention. Enterprise products usually churn far less.
- Gross margin: 70–80% or more is normal for software. Lower margins often point to heavy hosting, payment or service costs.
- LTV:CAC: 3:1 is the usual rule of thumb. Below 1:1 you lose money on every customer. Well above 5:1 can mean you are underinvesting in growth.
- CAC payback: under 12 months is the common target. Products with large contracts often accept longer.
Common mistakes
- Leaving costs out of CAC. Include salaries, agency fees and tools, not only ad spend.
- Using revenue instead of gross profit for LTV. Revenue LTV flatters the ratio by the size of your cost of sales.
- Counting new customers in churn. Churn divides by customers at the start of the month only.
- Judging on one month. A single bad month of churn swings LTV a lot. Check the trend over three to six months.
- Treating MRR growth as health. Fast MRR growth with high churn and slow payback can burn cash quickly.
How to improve your weakest metric
- Churn: fix onboarding first. Most avoidable cancellations happen in the first 90 days. In the example, a quarter fewer cancellations (2% churn) lifts LTV to $10,000 and LTV:CAC to 5.6:1.
- Gross margin: review hosting, third-party fees and support cost per account.
- LTV:CAC: move spend towards channels with lower CAC, such as search, referrals and outbound to a tight list, or raise prices.
- CAC payback: offer annual prepaid plans, push expansion revenue early and cut spend on channels that bring low-value customers.
Related tools
Go deeper on one metric with the MRR Calculator, the Churn Rate Calculator and the SaaS LTV Calculator, or check cost of sales with the SaaS Gross Margin Calculator. If CAC is your weak spot, our SEO services build a channel that keeps bringing in customers without paying for every click.