Locks that work

The Abus Granit X 54's 13mm square shackle is approximately 15mm in diameter, corner to corner.

Do you want to know the exact calculations for the cross sectional area? Finding area of a circle using... Area=(Pi)r²

13mm round = 132.732mm²
13mm square = 169mm² (27.3% greater than 13mm round)

Finding the diameter for a given cross sectional area, X, using... Diameter=2*(square root(X/Pi))

169mm² = 14.669mm round

So to sum up and assuming all else is equal...

• A 13mm square shackle is 27% 'tougher' than a 13mm round shackle.
  
• A 13mm square shackle would be equivalent to a 14.7mm round shackle.