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The baseplate's overall length (long side).
The plate the pattern has to live inside. Two things have to fit, not one: the edge distance required from every bolt to the plate edge, and the physical room to get a spanner or an impact socket onto each nut. A pattern that is geometrically correct and cannot be tightened is not a pattern — and it is discovered by the erector, on site, with the steel already hanging.
The baseplate's overall width (short side).
The short side, and the one that runs out first. Edge distance is required in both directions, so this dimension sets the tighter of the two constraints, and it is the direction in which a pattern gets squeezed toward the column flange where the wrench cannot reach anyway. When it does not fit, the correct answer is a larger plate rather than a reduced edge distance — the edge distance is what stops the concrete breaking out.
The maximum allowable spacing between anchor bolts around the perimeter.
Set by the baseplate design (edge distance and bearing requirements) from the structural engineer's drawings.
How far the centre of a corner rod is held back from the plate edge.
The figure from the drawing, not one this page derives. It is what turns a plate dimension into a run the bolts can actually be spaced along, and it is set by three things at once: the hole in the plate, which for an anchor rod is heavily oversized; the washer that has to cover that hole; and the reach of whatever tightens the nut. Enter zero to see the layout this page returned before the edge distance existed — rods sitting on the plate corners, which is a pattern no fabricator will drill.
Total anchor bolts
10 anchor bolts
- Bolts per long side
- 4
- Bolts per short side
- 3
- Pitch along each long side
- 0.56 ft
- Pitch across each short side
- 0.5 ft
They open the calculator with your figures already in it
Baseplate Anchor Bolt Pattern Layout Calculator: 10 anchor bolts — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- For a rectangular perimeter anchor pattern, the run available on a side is the plate dimension less twice the edge distance: bolts along each long side = ceil((plate length − 2×edge distance) ÷ max spacing) + 1, bolts along each short side the same on the width; total = 2×(long-side count) + 2×(short-side count − 2), avoiding double-counting the 4 corner bolts
- The pitch to set out from is that run divided by one less than the bolts on the side, which is at or below the maximum entered and is not the maximum itself
Inputs used
- Baseplate Length
- 2 ft
- Baseplate Width
- 16 in
- Maximum Bolt Spacing
- 9.75 in
- Edge Distance to the Corner Rods
- 2 in
Intermediate steps
- Bolts per long side
- 4
- Bolts per short side
- 3
- Pitch along each long side
- 0.56 ft
- Pitch across each short side
- 0.5 ft
What this calculation does not cover
- The pattern assumed here is a uniform run of rods along all four plate edges. Many column bases instead put rods only outside the flanges in two rows, and a rod that this layout places behind the column section, a stiffener or a shear lug may have no room for a socket or spanner. The calculator does not check wrench access or clashes with the column profile.
- The only rule applied is the maximum spacing you enter, but anchor rod groups are normally governed by the opposite limit. Rods placed too close together have overlapping concrete breakout cones, which cuts the tension capacity of the group well below the sum of the individual rods, and distance to the concrete edge controls the same failure. Enter a small maximum spacing and this page will return a dense pattern with nothing checking that the rods are far enough apart, or far enough from the concrete edge, to develop their capacity; those minima come from the anchor design, typically ACI 318 Chapter 17.
- The edge distance is taken as given and is never checked. It is the figure that has to satisfy the plate — an oversized hole, a washer covering it, and a socket that can reach the nut — and separately the concrete, where distance to a pier face is what stops a breakout cone forming. Those are different numbers from different codes, and the larger of them governs; this page divides by whichever one you type.
- The two pitches are even divisions of each side, so they sit at or below the maximum rather than on it, and the long and short sides will usually differ from each other. Neither is a gauge line across the plate: the rods on the two long sides face each other at the plate width less twice the edge distance, and that cross dimension, along with which rod is the datum, still has to be put on the drawing by hand.
- Nothing about the rods themselves comes out of this calculation: no diameter, embedment depth, projection above the grout line, thread length, baseplate hole size or washer type. The number is also a pattern count rather than a purchase quantity, so it carries no spares for bent or misplaced rods, no template rods, and no levelling or double nuts.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-19 · v1.1.0
Regulatory standards & verification citations2
- For a rectangular perimeter anchor pattern, the run available on a side is the plate dimension less twice the edge distance: bolts along each long side = ceil((plate length − 2×edge distance) ÷ max spacing) + 1, bolts along each short side the same on the width; total = 2×(long-side count) + 2×(short-side count − 2), avoiding double-counting the 4 corner bolts
- The pitch to set out from is that run divided by one less than the bolts on the side, which is at or below the maximum entered and is not the maximum itself
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
Full-size anchor rod templates
Print the setting template the rods are cast through, cut to the plate with a hole for every rod and the centrelines to line up with the grid, or the plate's drilling layout to punch — with the cross dimension between the rows the drawing usually leaves to hand, and a calibration square on every sheet.