How to use of Meters and numbers in inventory

Dear Sir,
My business is online sale of Fabrics. When we buy fabric it is in Meters and number of suits like when we buy 80 Meter Fabric that is 20 suits, 1 suit is = 4 meter. When we sold Some time customer demand 1 suit of 6 meter. How can we booked doubl unit of quatity.
Can you add manual calculation in measure of unit or other way to resolve this issue?
Thanks
Shahid

Use production orders. So you produce suits with 6m and with 4m,. See the guides at Use production orders to manufacture inventory items | Manager

When still questions first search the forum (magnifier) because this has been extensively discussed and explained.

This capability already exists for all number fields in Manager. The Guides explain this.