Car Lease Calculator Software, free software download. Leasetrader.com Car Lease Calculator Software is a freeware tool that allows you to calculate the monthly lease payment and the overall lease costs. Step-by-step through a few easy questions about the lease. Then we`ll analyze your answers and give you your results instantly. Use this calculator to analyze any lease deal: Find monthly payments, calculate total lease costs, discover hidden fees, and check dealers` figures. 1.