CTC Breakup Calculation

Dear All,
I would like to know the clear information about the Compensation Breackup head and its calculation methods. I am in chennai(metro). We have the components like Basic, HRA,Special Allownace, Conveyance Allwance, Medical Allowance and PF, incase of ESI we add that too..
Please let me know how to arrive the values by using the percentages which is allowed/approved as per law. Pls do share such law information also for reference.
If you could send in Excel would he really Great. Because I am planing to create a calculated to know the exact Take home. which will help me during salary negotiations.

Dear Ramesh
Pls calculate total earnings and after the deduction in your salary what your getting (Ex; After PF and ESI) only + any statutary deduction like Proffessional Tax or State Welfare fund like that.
2). You want to know How the break ups like Conveyance + Medical + HRA
from your tax prespective Medical 1250/- Per month exemted from deduction of tax
Conveyance 1600/- Per Month Exempeted from the tax
HRA also comes under exeption of payable tax
Mohandas M