No, you do NOT have to file if the money held in the foreign account is $10k or less when it is converted to US DOLLARS:
Example: you have 10,500 in foreign currency, but when you convert that to US Dollars the amount is $9,800.00 in US DOLLARS then NO you do not have to file FBAR because it is not more than $10,000.00 US dollars.
But if when you convert 9,800 in foreign currency into US Dollars and the US Dollar value is $10,500.00 then YES you would file FBAR because it is over $10,000.00 USD.
The IRS is only interested in account values of OVER $10,000 in US dollars, they don't care what the foreign currency value is, they only care what the US DOLLAR VALUE is.
You would use
They literally say "$10,000" which is US DOLLARS, the IRS is not interested in the value in foreign currency, just what the value of that foreign currency is in US DOLLARS. So you would need to report any value worth over $10,000 US DOLLARS. So you'd have to calculate
The IRS is only interested if it is the value of any amount that exceeds the value of $10,000 US DOLLARS regardless if the foreign currency calculates less when converted from US DOLLARS.
Example: you have €9500.00 euro in an Italian bank, but the value of that in US dollars is $10,324.00 then YES you'd need to file FBAR because the value is over $10,000.00
Example: you have CHF 9,800.00 swiss francs in a Swiss bank, but the value of those francs in US dollars is $10,009.00 then YES you need to file FBAR because the value of what you have in the foreign bank is in fact over $10,000.00 US DOLLARS.
You would use the IRS conversion table for the year you are filing. Here--> scroll 1/4 way down on page:
https://www.irs.gov/individuals/international-taxpayers/yearly-average-currency-exchange-rates
If after you convert your foreign currency to USD and the USD is $10,000.00 or less you do NOT file FBAR,
If after you convert your foreign currency to USD and the USD is OVER $10,000.00 you DO file an FBAR
