[Discovery SII TD5] What gear ratio to compensate 32" ?

Tire size calculator

This is great to work out tyre sizes.

P.S. I have 32's and found the Mud tyres a bit underpowered in sand... installed a remap by Toombie and it felt better than when running on original tyres.;)

That's really handy thanks. So, the 275/65/18 turns out to be 32.1"and that is an increase of 10.1% over stock. Even though my d2 td5 has been mapped I still feel shorter gearing will be needed.