Monthly volume at ~$190 billion [2], as compared to ~$1 trillion monthly volume for Visa globally [3].
Pretty good, given that most banks have daily UPI limits of $1200, and much lower individual transaction limits.
[1] https://www.thenationalnews.com/business/technology/2023/07/...
[2] https://www.cnbctv18.com/technology/upi-monthly-transaction-...
[3] https://annualreport.visa.com/financials/default.aspx