What size anchor bolts are required by code?

The IRC requires a minimum 1/2-inch diameter anchor bolt embedded at least 7 inches into concrete, spaced no more than 6 feet apart.

Do I need anchor bolts at every corner?

Yes. Place an anchor bolt within 12 inches of each end of every sill plate board and at every foundation corner.

Can I add anchor bolts after the concrete has cured?

Yes, using epoxy anchor bolts (Simpson SET or similar). These are drilled in and bonded with structural epoxy.

Anchor Bolt Calculator

Calculate how many anchor bolts you need for your foundation perimeter based on standard 6 ft spacing.

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Enter Your Measurements

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How to Use This Calculator

1Measure the total perimeter of your foundation in feet.
2Enter the standard spacing (default 6 ft per IRC code).
3Click Calculate to get the bolt count.

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About This Material

Anchor bolts (J-bolts) are embedded in the concrete foundation to secure the sill plate. The IRC requires anchor bolts every 6 feet and within 12 inches of corners.

Installation Tips

•Set bolts before concrete sets fully, while it is still workable.
•Use a template jig to maintain consistent spacing and alignment.
•Ensure bolts extend at least 7 inches into concrete.
•Place bolts within 12 inches of the end of each sill plate piece.

Common Mistakes to Avoid

Skipping bolts at board joints — always place one within 12" of each end.
Using the wrong bolt diameter — standard is 1/2" minimum.
Not checking plumb before concrete cures.