计量calculate n. /to find out how much something will cost, how long something will take etc, by using numbers 测量measure vt./to find the size, length, or amount of something, using standard units such as inch es ,metres etc

I feel 计量 is a noun, the phrase I can recall is 计量单位，a standard of measurement. And it occurs in the situation that related with scientific research more. It is also a verb for 精确计量, also for research or engineering. Simple 计量 is not often seen I feel. 测量, maybe used in primary school students' book. Not very oral, but it is used in daily situation, not so professional. And the oral one is 量。量一下有多长。measure how long it is.

I think one is to measure things very accurately and often used in laboratory 测量 is used to measure larger things in daily life

计量 is more professional

The first thing that comes to my mind when I hear "计量" is "metrology" or "econometrics". We seldom use it in everyday life. At least I don't hear it very often. "测量" means "to measure". Eg: 测量身高/体重, to measure the height/weight.