Display Currency & FX Rates

Public per-card GBP values are currently withheld. The FX service still maintains rates for six display currencies, but those rates do not reveal or reconstruct a withheld card value. Where an active transaction surface supplies a GBP amount, currency conversion is a display transform only; this page does not claim that every commerce flow is currently available.

The six currencies

The selector covers the platform's real audiences today. Each is ISO 4217.

Where the rates come from

We fetch the European Central Bank's daily EUR reference rates, cached for six hours. The ECB permits free commercial and non-commercial reuse of its public statistics when the source is quoted.

1. Source: Source: ECB statistics. The source file is EUR-base; Cambridge computes each GBP-base rate as target_per_EUR / GBP_per_EUR and labels that transformation in the API response.
2. Final fallback: a static rate table baked into the storefront, refreshed by the developer on platform releases. When this is in play, the surface shows an amber "fallback"pill so visitors aren't misled.

Independently of the withheld card values, the FX-rate service is currently reading from ecb.europa.eu, observed as of 2026-08-07T00:00:00.000Z and fetched at 2026-08-08T20:54:58.354Z.

The conversion math

For a card priced at p GBP and a target currency c with a rate r(c) expressed as units of c per 1 GBP:

displayValue = p × r(c)
displayString = format(displayValue, locale(c), decimals(c))

GBP is the base, so r(GBP) = 1.0 exactly. JPY uses zero decimal places; the other five use two.

Why this is display-only

Three reasons we don't accept transactions in non-GBP currencies:

• Settlement risk.The platform's bank is in GBP. Accepting USD or JPY at the checkout would require us to either hedge the exposure or pass it to the customer with a spread — both of which add complexity without changing the price.
• VAT compliance. UK VAT must be calculated in GBP on the date of supply. Multi-currency checkout would require a second VAT engine.
• Refund symmetry. A refund in a different currency than the original charge creates an FX gain/loss for the customer, which is hostile to the trade-in flow especially.

The display selector exists because readinga price in your own currency is useful — it's the action of converting that we want to keep in one place (the bank).

Machine-readable surface

The rate table is available as JSON at /api/v1/fx-rates with the standard data-pantry envelope, NOASSERTION aggregate license, ECB attribution, observation date, retrieval time, and exact GBP-base transformation. The former open.er-api.com and exchangerate.host paths were retired because their terms do not grant Cambridge a public rate-table redistribution right.

What we don't do

• We don't price-discriminate by currency. The selector is symmetric — a Japanese visitor sees the same GBP base price as a British visitor, just rendered in JPY.
• We don't add an FX margin to the display rate. Mid-market in, mid-market out. The platform earns its margin on the card price, not the FX.
• We don't cache rates per-user. Everyone reads the same rate table; if your conversion looks off, refresh — the cache is six hours.

Related surfaces

• /methodology/pricing — how the GBP base price itself is computed (upstream JPY → GBP, channel uplift, VAT, margin).
• /methodology/cross-source-pricing — how we compose USD / EUR / JPY signals from multiple upstreams into a single comparable view.
• /api/v1/fx-rates — the machine-readable rate table.
• /prices — the price guide itself, where the selector lives.