How to calculate percentage improvement in response time for performance testing

Question

How should I calculate the percentage improvement in response time.

I am getting 15306 ms response time for old code and 799 ms response for th

Answer 1

your code's runtime is 94.78% shorter/improved/decreased:

(new - old) / old x 100%
(799 - 15306) / 15306 x 100% =~ -94.78% (minus represents decrease)

your code is 1816% faster:

(old - new) / new x 100%
(15306 - 799) / 799 x 100% =~ 1816%