No one actually knows how to lculate what speaker cable they need

Vtl 250 mono blocks,  speaker is Gradient 1.3  they are 4 feet away from amp,  thank you

All this is eye-of-newt-and-toe-of-frog. Get good, rationally-engineered, not-too-expensive cables (I use Blue Jeans), and keep them matched in length and reasonably short.

Mr. fedie
Your  Vtl 250 mono blocks have a DF of 9.3! (8 ohms / 0.86).
https://www.stereophile.com/content/vtl-225w-deluxe-monoblock-power-amplifier-measurements
At 4' you may use almost any wire. it won't make any difference.

Mr. kosst_amojan

There is nothing in your observation to disapprove nor approve anything. 

I'll use Confucius say:

The one who asks a question, may look fool for a few minutes. The one who don't, will remain fool for the rest of his lives.

This has got to be one of the dumbest threads ever created around the subject of cables.

I read through every single post, holding back laughing and crying the entire time. The OP of this thread doesn’t have the first idea about the science behind the transmission of amplified sound. Instead of wasting my time explaining to you all what is wrong with these posts... you can start down the road of real understanding by reading this-
http://www.roger-russell.com/wire/wire.htm