I am using magento table rates Weight vs Destination for shipping method. I have added weight up to 3 kg and shipping price according to that. It is working fine. But above 3 kg the shipping price will be INR 25 per KG. For example if the weight will be 5 KG then the shipping price will be 5 x INR 25 = INR 125 How to achieve that in Table Rate.
I'm afraid it's not possible with the magento default table rate.
You can either create a new shipping module that implements your weight logic, see the tutorial http://www.magentocommerce.com/wiki/5_-_modules_and_development/shipping/create-shipping-method-module
Or use some extension, like shipping table rates from the magento connect.