The volume of a 20kg bag of concrete can vary based on the density of the concrete mix. However, a common approximation is that a 20kg bag of concrete yields about 0.009 cubic meters (m3) or 9 liters of concrete when mixed with water.

In general, a 20kg bag of concrete is about 9 liters, a 25kg bag of concrete is about 11.5 liters, a 30kg bag of concrete is about 13.6 liters, and a 40kg bag of concrete is about 18 liters.

The density or unit mass of pre-mix bag of concrete is about 2200 kilograms per cubic meter (kg/m3), which means one cubic meter of concrete weighs about 2,200 kg, so volume of a 20kg bag of pre-mix concrete = 20/2200 = 0.009 m3, or which is equivalent to about 9 Liters of concrete.

To calculate the volume of a 20kg bag of concrete in liters, multiply its yields in cubic meters by 1000 (since 1 m3 = 1000 liters)). To find out volume of concrete bag in cubic meters, you can divide weight of a concrete bag in kg by 2200 (since, 1 m3 pre-mix concrete weight = 2,200 kg).

Formula to convert cubic meter of concrete to liters: write down the volume expressed in cubic meters. Multiply this number by 1000 to convert to liters. So, one meter of concrete converted to liters equals to 1000 liters.

For example, a 20kg bag of concrete mix can produce about 0.32 cubic feet of concrete, which is equivalent to about 0.009 cubic meters or 9 liters of concrete. Volume of a 20kg bag of concrete in cubic meter = 20/2200 = 0.009 cubic meters, and volume in liters = 0.009 × 1000 = 9 liters.

A 25kg bag of concrete mix can produce about 0.40 cubic feet of concrete, which is equivalent to about 0.0114 cubic meters or 11.5 liters of concrete. Volume of a 25kg bag of concrete in cubic meter = 25/2200 = 0.0114 cubic meters, and volume in liters = 0.0114 × 1000 = 11.5 liters.

A 30kg bag of concrete mix can produce about 0.48 cubic feet of concrete, which is equivalent to about 0.0136 cubic meters or 13.6 liters of concrete. Volume of a 30kg bag of concrete in cubic meter = 30/2200 = 0.0136 cubic meters, and volume in liters = 0.0136 × 1000 = 13.6 liters.

A 40kg bag of concrete mix can produce about 0.64 cubic feet of concrete, which is equivalent to about 0.018 cubic meters or 18 liters of concrete. Volume of a 40kg bag of concrete in cubic meter = 40/2200 = 0.018 cubic meters, and volume in liters = 0.018 × 1000 = 18 liters.

**Conclusions:**

In general, a 20kg bag of concrete can make about 9 liters, a 25kg bag can make about 11.5 liters, a 30kg bag can make about 13.6 liters, and a 40kg bag of concrete can make about 18 liters.