Purchase of Material, if done within India (called Indigenous purchase) attracts taxes known as State Taxes, Central Taxes and Value Added Tax (VAT). The main duty components levied  by the government are Excise duty (ED) and Education cess on ED.

While estimating the price of an item , normally the ED is to be taken as 16% and the Education Cess (EC) as 2% on ED. It can be 16.32% straight while adding on the base price.

With the introduction of VAT ,wherever it is applicable , in place of Sales Tax, a factor of 12.50% without provision of 'C' form and 4% with the provision of 'C' form is to be taken into account. 'C' form can be provided for the material being consigned to the business entity that is selling goods and is thus registered with the Sales Tax authorities.
For example, if an item costs Rs X (100) then for arriving at the estimated  price the calculation shall be like this:

Base price = X (100)
Add ED & EC @16.32 %
Sub total (A)=X+(16.32x100/100)= 116.32

Calculate 4% or 12.50% on A= 116.32(4/100) = 4.65 (approx.) = B
or
116.32(12.50/100) = 14.25 (approx.)= B

Thus A+B = Rs 120.97 with 'C' form
or     A+B = Rs 130.56 without 'C ' form 

And don't forget to add 4% for Packing & Forwarding and Transportation on A+B !!
Thus your price estimate should be
130.56+( 130.56x5/100) = Rs 137

For purchasing services (AMC contracts etc.) the applicable tax is only the Service tax @12.25% on the base price
Thus for a base price of Rs P , the total estimated price shall be Rs P+(Px12.25/100)

It may be noted that in purchases where material and labour both are used all the taxes and duties described above can be applicable together.