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

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

**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/mc-currencies service or GET/ecb-currencies to access a list of currencies you wish to display.

   <br />

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/summary-rate service.

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

5. The Mastercard summary-rate Service returns the applicable

   * Mastercard currency conversion rate *conversionRate*
   * Cardholder billing amount with and without issuer fees *crdhldBillAmtExclAllFees / crdhldBillAmtInclAllFees*
   * European Central Bank (ECB) rate *ecbReferenceRateDate*
   * Effective exchange rate (includes fixed and percentage fees) *effectiveConversionRate*
   * Percentage difference between Mastercard and ECB exchange rates with and without issuer fees *pctDifferenceMastercardExclAllFeesAndEcb / pctDifferenceMastercardInclAllFeesAndEcb*
6. The Issuer's server sends the applicable data fields to be displayed on the Issuer's user interface.

Note: As an alternative, customers can call the API a maximum of x2 per day (upon Mastercard rates being updated and ECB rates being updated) per desired currency pair. Internalize the rate information for cardholder presentment until the rates are refreshed the next day.

## Next Steps {#next-steps}

|                                                                Category                                                                |                   Description                    |
|----------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------|
| [API Reference](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/api-reference/index.md)         | Try the Sandbox APIs directly from your browser. |
| [Reference Application](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/reference-app/index.md) | Reference Application that can be downloaded.    |
| [Parameters](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/parameters/index.md)               | Requests and responses for each endpoint.        |
| [Code and Formats](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/code-and-formats/index.md)   | Error codes and the formats we use.              |
| [Support](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/support/index.md)                     | FAQs and support.                                |