Estimation is the process of finding an estimate, or approximation, which is a value that can be used for some purpose even if input data may be incomplete, uncertain, or unstable.
Estimation determines how much money, effort, resources, and time it will take to build a specific system or product. Estimation is based on −
Past Data/Past Experience
The four basic steps in Software Project Estimation are −
Estimate the size of the development product.
Estimate the effort in person-months or person-hours.
Estimate the schedule in calendar months.
Estimate the project cost in agreed currency.