Private Residences Relief

When calculating the value of PRR for a property lived in but subsequently let, I'm assuming I use the "gain" figure that includes the cost of allowable renovations costs eg (as opposed to to using the gain figure excluding renovation costs) Purchase Price £100k Selling Price £200k Renovation Costs £50k Gain £50k

Hi,
Yes, it's on the gain after the deduction of costs.
Thank you.