Sir, how to calculate work in progress?

Work in progress cannot be calculated based on Bank Statments, but can be just estimated.

Actually, architect or inspecting authority certifies the work completed, and based on that Work in progress is calculated.

Sir, which amount or how  to analysis in bank statement to estimate the work in progress.Its is quite confusing.

For estimate: you can use simple method as follows:

Total Estimated project cost: say Rs.100.

Amount of Total materials to be used: say Rs. 80

Materials already used (as per payments from Bank statement): :say Rs. 60.

Thus estimated work in progress will be 75%