Crikey. I can't mental maths that. 
OK, so if the earth is 40,075km, then (assuming that's exact) that's 40,075,000m. Assuming also a perfect circle, the radius is therefore 6,378,134.34m. So if the radius is increased by 1m, then the circumference becomes 40,075,006.28m. So its 6.28 metres?
There's probably an easier way I could have worked that out.
Wait a sec... that like pi * 2 isn't it?
				
			OK, so if the earth is 40,075km, then (assuming that's exact) that's 40,075,000m. Assuming also a perfect circle, the radius is therefore 6,378,134.34m. So if the radius is increased by 1m, then the circumference becomes 40,075,006.28m. So its 6.28 metres?
There's probably an easier way I could have worked that out.
Wait a sec... that like pi * 2 isn't it?
 
				
		 
 
		 
 
		

 Some folks I knew used little cards, about A6 size, and swore by those.
 Some folks I knew used little cards, about A6 size, and swore by those.