Measurement Price Calculator for WooCommerce

Hi, the idea is that when a customer buys (for example) 1sqm of any material, I can set a €5 fixed fee for the cutting.

This happens on custom size product, where for certain materials there’s the need to take time to cut them, so it should be charged. For example, a 20cm x 20 cm material costs 2 euros, but I need a person that prepares it, so I shall charge €5 plus and the total is € 7. In the overage option, I could set a percentage but it would be, using 10% for example, 20cents when a person buys 2 euros and 20 euros when a person buys 200. This would be completely wrong.

The option should be in the backend, similar to the overage option check, but to input a precise amount.