1. Empirical formula for calculating the size of standard bolts and nuts (wrench size) (in the form of fractions):
Standard bolt and nut size (wrench size) = (bolt thread size numerator × 3) ÷ (bolt thread size numerator × 2)
For example: the wrench size corresponding to a standard bolt with 1/2 inch thread = (1×3)÷(2×2) inch = 3/4 inch
2. Empirical formula for calculating the size of weighted bolts and nuts (wrench size) (in the form of fractions):
Weighted bolt and nut size (wrench size) = standard bolt and nut size 1/8
For example: the wrench size corresponding to the weighted bolt with 1/2 inch thread = (1×3)÷(2×2) inch 1/8=7/8 inch
The wrench size corresponding to the hexagonal bolt:
4mm bolts use 7mm wrench; 5mm bolts use 8mm wrench;
6mm bolts use 10mm wrench; 8mm bolts use 12mm or 14mm;
10mm bolts use 17mm wrench; 12mm bolts use 19mm wrench;
14mm bolts use 22mm wrench; 16mm bolts use 24mm wrench;
18mm bolts use 27mm wrench; 20mm bolts use 30mm wrench;
22mm bolts use a 32mm wrench; 24mm bolts use a 36mm wrench;
For 27mm bolts, use 41mm spanner; 30mm bolts use 46mm spanner;
36mm bolts use 55mm wrenches; 42mm bolts use 65mm wrenches;