> For the complete index of the 402pay docs, see [llms.txt](https://402pay.co/docs/llms.txt).

# Amounts, currencies and exchange rates

How prices, US dollar reporting and coin amounts are written, and how one becomes another.

Three kinds of amount appear in the API: the price, in the currency you set; its value in US dollars, for reporting; and coin amounts, for what customers send and what reaches your wallet.

## Prices

A price is a decimal string in whole units of its `currency`, with two decimal places: `"49.00"` with `EUR` is €49.00. Every supported currency has two decimal places, so every fiat amount in a response is written that way, `"0.00"` for nothing and `"-3.00"` below zero. When you send a price, `"49.00"`, `"49.5"` and `"49"` are all accepted; a JSON number, or more than two decimal places, returns 400 `invalid_request`. Links and payments take any of these currencies, from the equivalent of $1.00 up to 1,000,000.00 in the currency. Card payment limits depend on the available route, currency and customer region.

| currency | Name | Example usd_rate | Example minimum | As amount |
| --- | --- | --- | --- | --- |
| `USD` | US dollar | 1 | $1.00 | `"1.00"` |
| `EUR` | Euro | 1.08 | €0.93 | `"0.93"` |
| `GBP` | British pound | 1.27 | £0.79 | `"0.79"` |
| `CAD` | Canadian dollar | 0.73 | CA$1.37 | `"1.37"` |
| `AUD` | Australian dollar | 0.66 | A$1.52 | `"1.52"` |

These rates and minimums are examples. The backend uses its current exchange rate to enforce the minimum price when you create or update a link.

The customer pays the price in its own currency, and the receipt shows it that way. A payment's `customer_fee` and `amount_received` are decimal strings in its `currency` too.

Read an amount with a decimal type, such as Python's `Decimal` or a `numeric` column, rather than a binary float, so sums stay exact to the cent.

## USD reporting

Everything you add up is in US dollars, as decimal strings: a payment's `reporting`, with its `amount`, `fee`, `customer_fee` and `net`, a link's `volume`, a customer's `stats`, [metrics](https://402pay.co/docs/api/metrics.md) (whose values are JSON numbers in whole dollars), and every `*_usd` field on the wallet. A price becomes US dollars at its currency's `usd_rate`, rounded to the nearest cent: €49.00 is 49.00 × 1.08 = `"52.92"`, or $52.92.

€49.00, as a payment reports it, Payment:

```json
{
  "amount": "49.00",
  "currency": "EUR",
  "fee_payer": "business",
  "customer_fee": "0.00",
  "amount_received": "0.00",
  "reporting": {
    "currency": "USD",
    "amount": "52.92",
    "fee": "0.00",
    "transaction_fee": "0.00",
    "customer_fee": "0.00",
    "net": "0.00"
  }
}
```

## Coin amounts

Coin amounts are decimal strings, such as `"52.92"`, so no precision is lost. Each coin is quoted to a fixed number of decimal places.

| asset | Name | Decimal places |
| --- | --- | --- |
| `USDC` | USD Coin | 2 |
| `USDT` | Tether | 2 |
| `BTC` | Bitcoin | 8 |
| `ETH` | Ethereum | 6 |
| `SOL` | Solana | 4 |
| `LTC` | Litecoin | 8 |
| `TRX` | Tron | 2 |

A checkout works out the coin amount from the price's US dollar value and the coin's price, rounded to the coin's decimal places, and shows the rate it used in `crypto.rate`: one coin in the price's currency, as a decimal string. Stablecoins count as one US dollar each.

€49.00, as a checkout quotes it, USDC:

```json
{
  "asset": "USDC",
  "network": "ethereum",
  "amount": "52.92",
  "rate": {
    "amount": "0.93",
    "currency": "EUR"
  }
}
```

€49.00, as a checkout quotes it, BTC:

```json
{
  "asset": "BTC",
  "network": "bitcoin",
  "amount": "0.00053780",
  "rate": {
    "amount": "91111.11",
    "currency": "EUR"
  }
}
```

- The checkout locks the amount and rate when it opens, for the quote window in your [checkout settings](https://402pay.co/docs/api/settings/retrieve.md), 15 minutes unless you change it.
- A payment's `method.amount` is what arrived in the coin, and `settlement.amount` what reached your wallet.
- A card payment reaches your wallet in the selected coin and network. Read its deposit in`settlement` for the delivered asset, network and amount, whatever the price's currency.

## Exchange rates

[`GET /exchange-rates`](https://402pay.co/docs/api/exchange-rates.md) returns the rates checkout quotes with: each coin's `price_usd`, a decimal string in US dollars, and each currency's `usd_rate`, a number of US dollars. It's public, so a page you build can show a price in coins before the customer opens a checkout.

> Coin prices follow the market, so read them when you need them rather than keeping a copy. A checkout's quote keeps the rate it opened with for its whole quote window.