Net mineral acres represent the true “net” acreage owned by a mineral owner out of the total gross acres in a given tract of land. NMA is calculated by multiplying the gross acreage by the owner’s undivided interest in the tract. If you own a 50% interest in the minerals under a 100-acre tract of land, you would own 50 net mineral acres (100GMA x 50% = 50NMA. The net mineral acres formula looks like this: Gross Mineral Acres x Interest Rate = Net Mineral Acres