Well are we talking 45s or LPs? If it is a 7", then on average the run in starts at approx 2.5mm from the edge, giving a starting radius from the centre of 85mm. The runout finishes at approx 8mm from the label, giving the radius at this point of 55mm.
Using the formula for the circumference of c=Pi*(2*radius) we find that the starting circumference is 534mm and the end circumference 346mm. For a record with an rpm of 45, and a nominal length of 3 minutes, then there would be 3*45=135 revolutions per track. Based on the *average circumference of (534+346)/2 = 440mm then the length of the groove if stretched out would be 440mm*135=59,400mm (59.4metres) or in old money 194' 10'' and a bit.
I hereby hang my anorak back on its peg!!!!