Customer Attrition Rate Calculator

Calculator

Customers at start

Starting active customers for the period.

Customers at end

Optional if you provide new and lost customers.

Lost customers

Customers who left during the period.

New customers

Used for inferring end customers and net attrition.

Calculation method

Pick the definition your team uses.

Segment label

Optional label for exports and reports.

Period unit

Used only for your own reference.

Periods per year

Annualized = 1 − (1 − period rate)^periods.

Include revenue rates

Optional revenue churn metrics for subscriptions.

Revenue inputs (optional)

Fill these only if you enabled revenue rates above.

Gross churn = (churn + contraction)/start

Starting revenue

Churned revenue

Contraction revenue

Expansion revenue

Ending revenue

Tip: Ending revenue can be left blank; it is not required for churn/retention rates above.

Clear

After submitting, results appear above this form under the header.

Example data table

Segment	Start Customers	New	Lost	End Customers	Average-base Attrition
SMB	1200	40	90	1150	90 ÷ ((1200+1150)/2) = 7.59%
Enterprise	220	12	8	224	8 ÷ ((220+224)/2) = 3.60%
All customers	1420	52	98	1374	98 ÷ ((1420+1374)/2) = 7.00%

Formula used

Start-base attrition: lost ÷ start
Average-base attrition: lost ÷ ((start + end) ÷ 2)
Net attrition: max(lost − new, 0) ÷ start
Retention: 1 − attrition
Annualized attrition: 1 − (1 − period_attrition)^(periods_per_year)
Gross revenue churn: (churned_revenue + contraction) ÷ starting_revenue
Net revenue churn: (churned_revenue + contraction − expansion) ÷ starting_revenue

How to use this calculator

Enter starting customers, and lost customers for your chosen period.
Add new customers if you want inferred ending customers or net attrition.
Optionally add ending customers to use the average-base method.
Select the method your organization uses for reporting.
Set periods per year to annualize results consistently.
Enable revenue rates if you track subscription revenue churn.
Press Calculate, then download CSV or PDF for sharing.

FAQs

1) What is customer attrition rate?

It measures the share of customers who stop buying or cancel during a period. Teams use it to monitor retention health and prioritize churn-reduction work.

2) Which denominator should I use?

Use start-base for simple reporting, average-base for smoother comparisons, and net attrition when new customers meaningfully offset losses. Pick one method and stay consistent.

3) Why annualize attrition?

Annualization makes rates comparable across different period lengths. It converts a period rate into an equivalent annual rate using compounding, which is more realistic than simple multiplication.

4) What if I do not know ending customers?

If you enter starting, new, and lost customers, the calculator infers ending customers as start + new − lost, never dropping below zero.

5) How is revenue churn different from customer attrition?

Customer attrition counts logos, while revenue churn measures lost recurring revenue. Expansion and contraction can change revenue even if customer counts stay stable.

6) Can net revenue retention exceed 100%?

Yes. If expansion revenue from existing customers exceeds churned and contraction revenue, net revenue retention can be above 100%, indicating strong upsell performance.

7) How often should I track attrition?

Monthly is common for subscriptions, while weekly may help high-volume businesses. Track frequently enough to spot changes early, but not so often that noise dominates trends.