Average Revenue Per User (ARPA)
The average monthly recurring revenue from a paying customer.
Compare month-to-month performance per customer. Estimate how many customers you need to reach and acquire to achieve a certain MRR. Get a crude overview of which plans/prices customers prefer.
Keep an upwards trend. No optimal value. The lower the ARPA, the more customers needed. Downwards trend ok when customers are moving to annual plans and long-term business value rises.
To Improve it:
Adjust plan pricing & marketing. Reduce downgrades, increase upgrades. Offer add-ons and related products to existing customers. Reduce refunds and discounts.
Customer Life-Time Value (CLTV)
MRR / Number of Paying Subscriptions
To get CLTV right, if you include non-paying customers to churn calculations, include them also to ARPA calculations.
In principle, ARPA seems to be a cover-all term for all per-unit revenue metrics.
Can also be calculated per segment e.g. ARPA for new customers, ARPA per plan For non-SaaS businesses, calculate it from revenue. For cost-profit comparisons, can include also free plan and trial customers. Can also be calculated per user/seat instead of customer/account/subscription.