OK - saving us all from a lot of maths

Exploring the calculation above will show that you have to reach 14% of the speed of light, or about 42 million m/s before you change the mass by 1%.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html#c3

As I said mystical irrelevant rubbish for normal Earth Dwellers.