Help calculating for my belt

I’m building my first diy MTB and have to determine the belts I will need. Motor mount says 90mm centers. Motor pulley is 20t and wheel pulley is 44t. This is where I got lost. Please find me and have a great day along the way to my discovery of trails and errors

Here’s another good one:

It doesn’t guide you through the process with auto-disabling options like the one on bbman but if you’re trying to run high gear ratios it’ll still give results. Remember that the belts you’ll use are 5mm pitch between teeth. Multiply number of teeth by 5 for circumference, divide circumference by pi for diameter. Distance between pulleys should be provided by motor mount makers.

Screenshot_20190526-130735 so according to this i would need a 345?

Also, not really the same topic but you guys might know. The speed calc used what to determine weight on the board?Screenshot_20190526-131321