While creating a payment intent, you have option to set the payment value in USD or Satoshi values. If you do not specify a unit, we use satoshi as a default unit. See our API Reference page for more details.
If you prefer to set payment values in USD terms, we use the most recent BTC/USD price for conversions.
Example: You create a payment with the value of $0.99. Based on the most recent BTC/USD price we calculate the Bitcoin equivalent in satoshi units (1 BTC = 100,000,000 satoshis).
This is to provide convenience for users who use USD as a unit of account. The actual payments are made in Satoshi terms.
Currently we use Bitstamp as our ticker source. We use volume weighted average price (VWAP) to avoid momentarily price spikes. We periodically update price information every 10 minutes.
If you have specific requirements about the currency rate calculations, please let us know.