Here are some examples of how it's used:
* The engineer's estimation of the construction costs was surprisingly accurate.
* The project manager requested an estimation of the time needed to complete the task.
* The company's estimation of its profits for the quarter was higher than expected.
You can also use the word "estimate" itself as a noun, but it usually refers to the actual number or value that has been estimated. For example:
* The estimate for the repairs was $500.
* The contractor provided a detailed estimate of the costs involved.