SaaS metrics calculator

A subscriber count of zero fails with invalid_input and is not billed, because both churn rate and lifetime value would divide by zero.

How MRR, churn rate, and customer lifetime value fall out of three numbers

Monthly recurring revenue, returned as mrr, is subscribers times price: the paying-customer count multiplied by the monthly price those customers pay, which is also average revenue per user when every subscriber sits on one plan. Churn rate is churned divided by subscribers: the share of the base that cancelled, expired, or otherwise left during the period. The calculator returns that ratio as churn_rate (zero to one) and as churn_rate_percent (zero to one hundred). Customer lifetime value is price divided by the monthly churn rate, which is the same as price times subscribers divided by churned: if five percent of the book leaves each month, a customer is expected to stay twenty months and contribute twenty times the monthly price.

Input contract, response shape, and error behaviour

Negative price and negative churned are rejected. When churned is zero the churn rate is zero and the lifetime fields are omitted rather than printed as infinity or null. POST a JSON body with three required finite numbers. subscribers is the customer count used as the base for the period — typically paying customers at the start of the month, or the current paying book you want to value — and must be strictly greater than zero; aliases customers, customer_count, and subscriber_count map to the same field so a worksheet can keep its column names. price is the monthly amount each subscriber pays, also called ARPU when the book is on one plan; aliases arpu, monthly_price, and price_per_subscriber are accepted. churned is how many customers left during the period; aliases churned_customers, cancelled, and churn_count are accepted. Each numeric field may arrive as a JSON number or a numeric string. Missing fields, empty strings, and non-finite values — NaN, Infinity, or text that does not parse as a number — fail with invalid_input naming the field. Those failures are not billed. A subscriber count of zero or a negative count also fails with invalid_input, because churn rate and lifetime value would divide by zero. Churned cannot exceed subscribers: a churn rate above one hundred percent is treated as a data error, not a result. On success the body echoes subscribers, price, and churned, then reports mrr as subscribers times price rounded half-up to two decimal places, arr as that monthly figure times twelve, churn_rate as churned divided by subscribers rounded half-up to eight decimal places, churn_rate_percent as that ratio times one hundred rounded half-up to six, customer_lifetime_months as subscribers divided by churned rounded half-up to four, customer_lifetime_value as price times subscribers divided by churned rounded half-up to two, plus a formula string restating the identities. Pair the JSON with your own rule for which subscriber snapshot matches the cancellations you send — starting count, ending count, or period average — because this endpoint divides the two numbers you send; it does not rebuild a billing ledger or choose a cohort convention. Pricing is a flat $0.002 per successful request.

Where a SaaS metrics calculator earns its keep

This is a different search and a different job from an exit-rate calculator that multiplies a given monthly revenue by twelve, from a combined loan-to-value calculator that sums liens against a property, and from a one-off revenue calculator that multiplies units sold by a transactional price: those tools start from different inputs and answer different questions.