{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"churn-rate"},"result":{"entity_type":"calculator","id":"churn-rate","calculator_id":"churn-rate","canonical_url":"https://tttkmbb.com/business/churn-rate","name":"Churn Rate Calculator","title":"Churn Rate Calculator – Customer Churn, Retention, Net Growth and Implied Customer Lifetime","category":"business","category_name":"Business & Marketing","tool_name":"calculate_churn_rate","featured_mcp_tool":false,"description":"Computes the customer churn rate for a period from customers at the start and customers lost, the retention rate, the ending customer count and net growth including customers gained, the annualised churn rate and the implied average customer lifetime (1 / churn).","use_when":"You track subscribers, members or accounts over a month, quarter or year and need churn, retention or expected customer lifetime.","do_not_use_when":"You need revenue churn in currency terms or MRR projections (use mrr-growth) or the full acquisition economics (use cac-ltv).","inputs":[{"name":"customers_at_start","label":"Customers at start of period","type":"integer","required":true,"max":1000000000000,"exclusive_min":0,"description":"Active customers on the first day of the period.","example":500},{"name":"customers_lost","label":"Customers lost","type":"integer","required":true,"min":0,"max":1000000000000,"description":"Customers who cancelled during the period (only those present at the start).","example":25},{"name":"customers_gained","label":"Customers gained","type":"integer","required":false,"default":0,"min":0,"max":1000000000000,"description":"New customers added during the period (excluded from the churn denominator).","example":60},{"name":"period","label":"Period length","type":"enum","required":false,"default":"month","values":[{"value":"month","label":"Month","aliases":["monthly"]},{"value":"quarter","label":"Quarter","aliases":["quarterly"]},{"value":"year","label":"Year","aliases":["annual","yearly"]}],"description":"Length of the measurement period; used to express lifetime in months and to annualise churn.","example":"month"}],"outputs":[{"name":"churn_rate_percent","label":"Churn rate","type":"number","unit":"%","decimals":2,"description":"customers_lost / customers_at_start × 100."},{"name":"retention_rate_percent","label":"Retention rate","type":"number","unit":"%","decimals":2,"description":"100 − churn rate."},{"name":"customers_at_end","label":"Customers at end","type":"integer","decimals":4,"description":"customers_at_start − customers_lost + customers_gained."},{"name":"net_growth_percent","label":"Net customer growth","type":"number","unit":"%","decimals":2,"description":"(customers_at_end − customers_at_start) / customers_at_start × 100."},{"name":"annualized_churn_percent","label":"Annualised churn","type":"number","unit":"%","decimals":2,"description":"100 × (1 − (1 − churn)^(12 / months in period))."},{"name":"average_customer_lifetime_periods","label":"Average customer lifetime","type":"number","unit":"periods","decimals":2,"description":"1 / churn rate, in periods (only when churn > 0)."},{"name":"average_customer_lifetime_months","label":"Average customer lifetime","type":"number","unit":"months","decimals":2,"description":"Lifetime converted to months (only when churn > 0)."}],"input_schema":{"type":"object","properties":{"customers_at_start":{"description":"Active customers on the first day of the period.","type":"integer","maximum":1000000000000,"exclusiveMinimum":0,"examples":[500]},"customers_lost":{"description":"Customers who cancelled during the period (only those present at the start).","type":"integer","minimum":0,"maximum":1000000000000,"examples":[25]},"customers_gained":{"description":"New customers added during the period (excluded from the churn denominator).","type":"integer","minimum":0,"maximum":1000000000000,"default":0,"examples":[60]},"period":{"description":"Length of the measurement period; used to express lifetime in months and to annualise churn.","type":"string","enum":["month","quarter","year"],"default":"month","examples":["month"]}},"additionalProperties":false,"required":["customers_at_start","customers_lost"]},"output_schema":{"type":"object","properties":{"churn_rate_percent":{"description":"customers_lost / customers_at_start × 100. Unit: %.","type":"number","x-unit":"%"},"retention_rate_percent":{"description":"100 − churn rate. Unit: %.","type":"number","x-unit":"%"},"customers_at_end":{"description":"customers_at_start − customers_lost + customers_gained.","type":"integer"},"net_growth_percent":{"description":"(customers_at_end − customers_at_start) / customers_at_start × 100. Unit: %.","type":"number","x-unit":"%"},"annualized_churn_percent":{"description":"100 × (1 − (1 − churn)^(12 / months in period)). Unit: %.","type":"number","x-unit":"%"},"average_customer_lifetime_periods":{"description":"1 / churn rate, in periods (only when churn > 0). Unit: periods.","type":"number","x-unit":"periods"},"average_customer_lifetime_months":{"description":"Lifetime converted to months (only when churn > 0). Unit: months.","type":"number","x-unit":"months"}}},"formula":"churn = customers_lost / customers_at_start; retention = 1 − churn; end = start − lost + gained; annualised churn = 1 − (1 − churn)^(12/m) with m = months per period; lifetime = 1 / churn","method":"Churn is measured against the customers present at the start of the period, so customers gained during the period are excluded from the denominator (the most common convention). Annualisation compounds retention.","sources":[{"name":"Wikipedia – Churn rate","url":"https://en.wikipedia.org/wiki/Churn_rate","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Customer retention","url":"https://en.wikipedia.org/wiki/Customer_retention","type":"reference","retrieved_at":"2026-09-24"},{"name":"Andreessen Horowitz – 16 Startup Metrics","url":"https://a16z.com/16-startup-metrics/","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"500 start, 25 lost, 60 gained (month)","inputs":{"customers_at_start":500,"customers_lost":25,"customers_gained":60,"period":"month"},"expected":{"churn_rate_percent":5,"retention_rate_percent":95,"customers_at_end":535,"net_growth_percent":7,"annualized_churn_percent":45.96,"average_customer_lifetime_periods":20,"average_customer_lifetime_months":20},"url":"https://tttkmbb.com/api/v1/calculate/churn-rate?customers_at_start=500&customers_lost=25&customers_gained=60&period=month"},{"name":"1,200 start, 90 lost (quarter)","inputs":{"customers_at_start":1200,"customers_lost":90,"period":"quarter"},"expected":{"churn_rate_percent":7.5,"retention_rate_percent":92.5,"customers_at_end":1110,"net_growth_percent":-7.5,"annualized_churn_percent":26.79,"average_customer_lifetime_periods":13.33,"average_customer_lifetime_months":40},"url":"https://tttkmbb.com/api/v1/calculate/churn-rate?customers_at_start=1200&customers_lost=90&period=quarter"}],"faq":[{"q":"Do new customers who leave in the same period count as churn?","a":"Not in this convention: churn counts only customers who existed at the start. Some companies use the average customer count as the denominator, which gives slightly different rates."},{"q":"Why is annualised churn not 12 × monthly churn?","a":"Because the base shrinks each month. 5 % monthly churn leaves 0.95^12 = 54 % of customers after a year, i.e. 46 % annual churn, not 60 %."}],"tags":["churn rate calculator","customer churn","retention rate","annualized churn","customer lifetime"],"related":[{"calculator_id":"cac-ltv","reason":"Turn churn into customer lifetime value."},{"calculator_id":"mrr-growth","reason":"Revenue-based growth including churned MRR."},{"calculator_id":"percentage-change","reason":"Plain percentage change between two counts."}],"links":{"html":"https://tttkmbb.com/business/churn-rate","markdown":"https://tttkmbb.com/business/churn-rate.md","json":"https://tttkmbb.com/business/churn-rate.json","api":"https://tttkmbb.com/api/v1/calculate/churn-rate","schema":"https://tttkmbb.com/api/v1/calculators/churn-rate","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T01:49:42Z"}