Free shipping threshold in converted currency

Store Design
1

I’m trying to offer free shipping on orders above a certain price threshold. E.g. I can set the free shipping threshold at £70.00. When my customer wants to check out in USD or EUR, what is the threshold for free shipping in their currency?

For example consider an exchange rate of 1.44 (which I get from the javascript Shopify.currency.rate). Naively, I thought it would be 70.00 * 1.44 = $100.80, but this isn’t the case as an order of $100 still triggers the free shippng rate I’ve set up. I feel like Shopify’s Payments system is using a different exchange rate to the theme.

The same issue exists for EUR too, but in the opposite direction. E.g. when converted to GBP the value is £71.50, but doesn’t trigger the free shipping condition.

This is causing such a headache, as without knowing how Shopify calculate this I’m unable to tell my customers what the threshold is for free shipping.

2

I know why this is now. I made a dummy “carrier” using the CarrierService API to see what information Shopify is using to determine the shipping thresholds.

It turns out the prices in the store currency are used to compute the shipping thresholds, so the foreign currencies are converted at checkout to the store currency. But the conversion here uses the automatic exchange rate (even if a manual one has been specified). This is probably a bug.