As per IS:456 2000 clause 6.2.3.1 Young's modulus generally used is 5000(fck)0.5. This average value is generally used. Accurate value will depend on many other factors such as percentage steel, type of steel, etc. Poisson's coefficient can be taken as 0.15. 

Thank you Dhirendra but the one specified in the code is only for either concrete or steel not the composite. What I want is Young's modulus for reinforced concrete. I do have all the percentage and grade of both steel and concrete. But I couldn't find way to calculate Young's modulus for reinforced concrete

You can calculate the properties of the composite along different directions  by simply using the mixture law. However reinforced concrete can rarely be considered homogeneous and isotropic, so calculating an average value of elastic parameters does not make sense in most situations. The concrete modulus is normally used, with the steel properties homogenized to the concrete ones.

Please refer the attachment, hope will be useful

The E value is a property of the material itself. Even in RC structures, the steel will still have its own W (200GPa) while concrete will also have its own value. Practically there is no unique value for Mod of elasticity of RC.

Concrete doesn't have linear stress-strain behavior. So we usually take the tangent modulus at one third of its ultimate stress (slope of line joining origin and the 1/3rd of maximum  stress) as its elastic modulus. Its poisson's depends on many factors any is not an unique value; usually it lies between .15 and .25

The Young's modulus of concrete can also be calculated by experimentally. It can be cross check with IS:456 2000.

There is not an accurate value. There is a range of expected values

Modulus of elasticity and poisson's ratio both can be calculated experimentally as per ASTM C-469 02 Tshering Delkar