In the US, when you buy bonds you tell the broker that you want 1, 10, 32, 1000, or whatever you decide on. Those are $1000 bonds, i.e., each bond has a face value of $1000. So if you buy 32, the face value is $32,000. That's all there is to it.
One thing that makes it seem more complicated is that the price for the bond is quoted as a percentage of face value. So if you see price of 98, you'll pay $980 for each bond. If the price is 110, you'll pay $1100 for each one. So if you buy 32 bonds at 98, you'll pay $32,000 x .98, which is $31,360.
Well, not quite. You also pay accumulated interest. Bonds usually pay interest every 6 months. If the bond paid interest one month before you bought it, it has accumulated 1 month of interest, which is owed to the seller. The bond issuer doesn't deal with that: you do. You pay 1 month of interest to the seller, in addition to the purchase price. So if the bond you're buying has a coupon rate of 6%, that's 1/2% per month, and your 32 bonds, having a face value of $32,000, have accumulated $160 in interest. So the price you pay is $31,360 plus $160 plus whatever the broker charges for commission.