Quick answer
Retention rate = (customers at end − new customers acquired) ÷ customers at start × 100. (1,100 − 200) ÷ 1,000 = 90%.
Enter the customers at the start and end of the period and the number of new customers. The calculator returns the retention rate.
Related tools: Churn Rate Calculator: Share of customers lost over a period. Net Revenue Retention Calculator: Net and gross revenue retention for a starting recurring-revenue base. Conversion Rate Calculator: Share of visitors who convert.
How to use the Retention Rate Calculator
- Enter customers at start (above 0).
- Enter customers at end (0 or more).
- Enter new customers acquired (0 or more).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Customers at start | A number | > 0 |
| Customers at end | A number | ≥ 0 |
| New customers acquired | A number | ≥ 0 |
Formula and method
Formula
retention = (end − new) ÷ start × 100
IEEE-754 double precision; shown to the decimals indicated.
Counts only customers who were present at the start.
Worked examples
This example is verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Customers at start = 1000; Customers at end = 1100; New customers acquired = 200.
| Result | Value |
|---|---|
| Retention rate | 90% |
The first line is the headline result (retention rate). IEEE-754 double precision; shown to the decimals indicated.
Why subtract new customers
The end count includes people who joined during the period. Removing them leaves only the customers who were there at the start and stayed: 900 of 1,000.
Churn and retention
Retention plus churn equals 100%, so a 90% retention rate means 10% churn. High retention lowers acquisition costs and raises lifetime value.
How the result changes with customers at start
Holding every other input at the first worked example, this table changes only customers at start. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Customers at start | Retention rate |
|---|---|
| 500 | 180% |
| 1000 | 90% |
| 2000 | 45% |
| 4000 | 22.5% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Customers at start: entering "0" shows "Customers at start must be greater than 0." beside that field and no result.
- New customers acquired: entering "9" shows "New customers cannot exceed the ending total." beside that field and no result.
Choosing between the Retention Rate Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Churn Rate Calculator](/business/churn-rate-calculator/) | customers lost and customers at start | Churn rate |
| [Net Revenue Retention Calculator](/business/nrr/) | starting recurring revenue, expansion revenue and contraction revenue | Net revenue retention |
| [Conversion Rate Calculator](/business/conversion-rate-calculator/) | conversions and visitors | Conversion rate |
| [Productivity Rate Calculator](/business/productivity-rate-calculator/) | output and input | Productivity |
| [Utilization Rate Calculator](/business/utilization-rate-calculator/) | billable hours and available hours | Utilization rate |
Background: business metrics
Business ratios depend on exactly which costs and revenues you include, so read each page's definition. Two common checks: break-even units = fixed costs ÷ (price − variable cost per unit), so $50,000 of fixed costs with a $10 price and $5 variable cost breaks even at 10,000 units; and net profit margin = net profit ÷ revenue, so $20,000 profit on $100,000 revenue is 20%.
Return on investment ignores time: 20% over five years is far less impressive than 20% in one, so compare returns over the same period.
Assumptions and limitations
- End minus new cannot be negative
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for customers at start and new customers acquired to confirm this.
Frequently asked questions
What is a good retention rate?
It depends on the business; subscription services often aim above 90% annually.
Can it exceed 100%?
Not with this formula.
What if end minus new is negative?
The calculator rejects it as inconsistent.
What does the Retention Rate Calculator calculate?
Customer retention over a period. It returns Retention rate.
What formula does the Retention Rate Calculator use?
retention = (end − new) ÷ start × 100. Counts only customers who were present at the start.
What do I need to enter in the retention Rate Calculator?
You enter Customers at start, Customers at end and New customers acquired.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. End minus new cannot be negative.
What is an example of a retention Rate result?
With customers at start 1000, customers at end 1100 and new customers acquired 200, the retention rate is 90%.
Related calculators
- Churn Rate Calculator — Share of customers lost over a period.
- Net Revenue Retention Calculator — Net and gross revenue retention for a starting recurring-revenue base.
- Conversion Rate Calculator — Share of visitors who convert.
- Productivity Rate Calculator — Productivity from output and input (hours, workers or cost).
- Utilization Rate Calculator — Billable hours as a share of available hours.
Sources
- Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.