# ARR Calculator & How to calculate ARR

[ARR (annual recurring revenue)](https://fund-forecasting@carta.com/learn/startups/metrics/arr/) is a key calculation that estimates expected revenue from new and existing subscription-based services or products over a 12-month period. The formula for ARR takes consistent revenue inflows and outflows into account and can be used to forecast future growth.

## ARR Calculator

Carta’s free ARR calculator automatically calculates ARR and MRR (monthly recurring revenue) for your company based on:

- Revenue from existing annual subscriptions
- New revenue from new annual customers
- Revenue from upgrades and add-ons
- Lost revenue from downgrades
- Lost revenue from customer churn

**Download the ARR calculator to get started.**