# Use Cases
source: https://developer.mastercard.com/currency-conversion-calculator/documentation/use-cases/index.md

This section provides a sample use case on implementing the **Standard Currency Converter Calculator** to create a mobile app or web-page that allows cardholders to view daily currency conversion rates applicable for their card transactions.
Diagram usecase

**The Sequence of steps for this operation:**

1. The cardholder logs into the issuing bank website or mobile app and provides transaction details including transaction amount and transaction currency.

   Tip: Consider providing a drop down list where a cardholder can select the transaction currency. You can use the `GET/settlement-currencies` service to access a list of currencies available.
2. Issuer validates the information entered by the customer and populates cardholder billing currency and bank fee (if applicable).

   Tip: You can either request the cardholder to provide all the transaction information including cardholder billing currency and bank fee or populate based on cardholders profile.
3. Issuer's server sends the transaction information to Mastercard Currency Conversion Service via `GET/conversion-rate`.

   Tip: You can enter 0000-00-00 in the `fxDate` parameter to retrieve the effective rates at the time of the request.
4. The Mastercard Conversion Rate Service retrieves information applicable to the currency pair.   

5. The Mastercard Conversion Rate Service returns the currency conversion rate `conversionRate` and cardholder billing amount `crdhlBillAmt` in response.   

6. The Issuer's server sends the data to be displayed on the Issuer's user interface.

## Next Steps {#next-steps}

|                                                                           Category                                                                            |                    Description                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------|
| [API Reference](https://developer.mastercard.com/currency-conversion-calculator/documentation/api-reference/index.md)                                         | Try the Sandbox APIs directly from your browser.   |
| [Reference Application](https://developer.mastercard.com/currency-conversion-calculator/documentation/reference-app/index.md)                                 | Reference Application that can be downloaded.      |
| [Parameters](https://developer.mastercard.com/currency-conversion-calculator/documentation/parameters/index.md)                                               | Requests and responses for each endpoint.          |
| [HTTP Response codes](https://developer.mastercard.com/currency-conversion-calculator/documentation/code-and-formats/index.md#http-response-and-reason-codes) | Detailed descriptions on HTTP codes and structure. |