Definition
Benchmark number
A benchmark number is a familiar reference number used to estimate, compare, or calculate.
What it means
A benchmark number is a number you know well and can use as a nearby signpost. Multiples of 10 help with whole-number estimates, while 0, 1/2, and 1 often help with fractions. Choose the signpost that makes the question easier.
Remember it
Use a familiar number as a signpost.
Example
To estimate 198 + 304, use 200 and 300 as benchmark numbers. Then 200 + 300 = 500, so the exact sum should be close to 500. Calculating exactly gives 502, which fits the estimate.
Watch for
A benchmark number is not one fixed number and is not automatically the nearest ten. Its usefulness depends on what you are estimating or comparing.
Common mix-up
The benchmark is the reference you choose; a rounded number or final estimate is the result you make using that reference.
Exact meaning
A benchmark number is a familiar, useful numerical value chosen as a reference for estimating, comparing, locating, or simplifying a calculation; the best benchmark depends on the task.