Structural Bolt Grip Calculator
Convert connection grip into an orderable bolt length. Adds heavy hex nut height, F436 washer thickness, and stick-out, then rounds to the increments fabricators stock.
Bolt Grip & Length
Includes 1/4" stick-out allowance.
Ordering Bolt Length from Grip
On a connection schedule, “grip” is the thickness of steel plies being clamped — not the bolt length itself. Detailing practice adds washer stack, heavy hex nut height, and enough stick-out past the nut so threads are fully engaged after galvanizing or paint build-up. Short bolts that barely catch the nut are a common field reject; this calculator builds in a 1/4″ stick-out allowance.
How to use this calculator
- Select bolt diameter (A325/A490 heavy hex sizes from 1/2″ through 1-1/4″).
- Enter total steel thickness through the connection — beam flange + angle + filler plates, measured along the bolt axis.
- Choose washer count (one F436 under the nut is typical; two when both sides need hardened washers or DTIs displace a washer).
Fabricator rounding
Bolts are not purchased to three decimals. Lengths up to 6″ round up to the next 1/4″; longer bolts round to 1/2″ stock steps. Always verify thread length vs. grip for TC bolts and snug-tight connections where the shear plane must stay in the shank.
FAQ
Does grip include the nut and washers?
Enter steel plies only. The tool adds F436 washer thickness and heavy hex nut height automatically.
What about direct-tension-indicator (DTI) washers?
Treat a DTI as an extra washer thickness in the count, or add its published thickness to the steel grip if you are modeling a special stack-up.
Will galvanizing change the required length?
Hot-dip galvanizing can add coating thickness and make threads tighter. Many shops keep the 1/4″ stick-out; for thick multi-ply joints, check RCSC recommendations and consider a trial assembly.
Why round up instead of to the nearest length?
Undersized bolts fail inspection. Rounding up to stock increments avoids short bolts while matching how distributors inventory A325/A490.