# Concrete - Water to Cement Ratios

## Water vs. cement ratio when mixing concrete.

Water to cement ratio is the ratio of

*weight of water* to the *weight of cement*

used in a concrete mix and can be expressed as

*r = w _{h20} / w_{c} *

* = 8.33 q _{H20} / w_{c} (1)*

*where *

*r = water to cement ratio*

* w_{h20 }= weight of water (lbs)*

* w_{c }= weight of cement (lbs)*

* q_{H20 }= volume of water (US gallon)*

### Example - Water to Cement Ratio

A batch of concrete has 45 gallons of water and 900 lbs of cement. The water to cement ratio can be calculated as

*r = **8.33 (45 gallons) / (900 lbs)*

* = 0.42 *