How are units of measurement chosen and interpreted in formulas?

Unit of measurement in a formula suggests a definite magnitude of a certain quantity. For instance, there are basic unit of measurement for the 7 basic quantities: These are
1. seconds (s) for time
2. meter (m) for length
3. candela (cd) for luminous intensity
4. Ampere (A) for electric current
5. Kelvin (K) for Temperature
6. Kilogram (kg) for mass
7. mole (mol) for amount of substance
These units of measure should be homogenous in a formula for easy interpretation. Other derived quantities (e.g volume) also have their corresponding units as well as those quantities which are not based on the metric systems (e.g Celsius, pounds, etc)