Estimator (noun)

1. A person or tool that estimates or calculates the value, number, or size of something.
2. A mathematical function used to estimate a desired quantity from observed data.

Origin:

From french estimateur, from latin aestimatus, past participle of aestimare ("to estimate"), from aes ("bronze, copper") + timare ("to value").

Examples:

1. The contractor used an estimator to calculate the cost of the renovation project.
2. The software program acted as an estimator, providing accurate predictions for sales revenue.
3. The surveyor acted as an estimator, determining the value of the property.
4. The statistician used an estimator to determine the population mean from a sample.
5. The engineer used an estimator to predict the strength of the structure under different loads.