Question

does anyone know how do i estimate depreciation expense for a company ?

Answer 1

Simple depreciation = (Purchase value - Salvage value)/ life of asset.

There are methods of accelerated depreciation and MACRS but I am not sure what you are specifically looking for.

Answer 2

Adding on from what siddiquera posted, if you only have the financial statement to work with (like most of us), you can estimate this years' Dep Expense using past year's
(Dep Expense/Total Depreciable Asset) * Depreciable asset

Probably giving what information you have would help us devise a way to estimate.