Why isn't there a simple universal formula for masonry anchor capacity, unlike concrete?

Because masonry anchor capacity depends heavily on the specific block's material properties, face shell thickness, and whether cells are grouted, unlike concrete, which has the well-established ACI 318 breakout formula. Manufacturers establish rated capacities through actual physical testing (ICC-ES evaluation reports) rather than a general calculable formula.

Is linear scaling with embedment depth accurate?

It's a rough approximation useful for a first estimate — actual capacity-vs-embedment relationships in masonry are often non-linear, especially near the face shell thickness limit, so always check whether the manufacturer publishes rated capacity at your specific embedment depth directly instead of scaling.

What if my embedment is deeper than any tested value?

Never extrapolate beyond the manufacturer's tested range, and this page will not do it for you: enter a depth greater than the rated one and it returns the rated capacity unchanged, with a note saying why. Capacity does not keep rising linearly past the tested depth — it flattens as the failure mode moves out of the anchor and into the block — so the honest answer at an untested depth is the last depth that was tested. Contact the manufacturer, or pick the report row that matches what you are installing.

Does drilling deeper into a hollow block help?

Not by itself. Past the face shell — about 32 mm on a standard unit — the hole is in a void, and depth in air carries nothing. What holds a fixing in an ungrouted cell is the face shell plus whatever the sleeve, toggle or screw geometry does behind it, and that is a property of the product rather than of the depth. If the load matters, grout the cell the anchor lands in, or choose a fixing whose evaluation report rates it for hollow block and use that report's figure directly.

Can I use this figure as the design capacity for a fixing that carries load?

No. The page multiplies your rated number by the ratio of two depths and stops there — no safety factor, no reduction for edge distance or anchor spacing, and no way to tell whether what you typed was an ultimate test load or an already-reduced working load, so the answer comes back on whatever basis you fed in. It also cannot tell tension from shear: it will scale either, and a fixing pulled and sheared at once is checked against the interaction rule the manufacturer publishes, not by scaling one number. That is why every result here is flagged low confidence, however small the change in depth. Use it to decide whether a product is worth looking up properly; once the fixing holds something you would not want to fall, the value that goes on the drawing is the manufacturer's tabulated capacity for your actual embedment, block type and edge distance, accepted by the engineer responsible for the connection.

Which depth goes in the boxes — the anchor length, or the depth I drill?

Neither, unless they happen to coincide. Embedment is the depth into the masonry itself, measured from the face of the block, so anything the anchor crosses on the way in — the bracket or ledger, a packing shim, a render or plaster coat — comes off first, and there is no field here for fixture thickness. Drilled depth is not it either: hole depth is whatever that anchor's installation instructions call for, which for many mechanical anchors is deeper than the embedment so the anchor can seat, and for a bonded anchor is the embedment itself in a hole cleaned out afterwards. Either way it is a different number from the depth the capacity was rated at. The other trap is mixing sources: the capacity and the reference depth have to come from the same row of the same table, because a grouted-cell capacity over a hollow-block reference depth is a ratio between two conditions that were never tested together. The depths the page opens with — 75 mm and 100 mm in metric, 3 in and 4 in in imperial, the imperial pair being the metric one converted and then rounded to the nearest quarter inch, which is why 3 in is not exactly 75 mm — exist to show the arithmetic working, not to suggest a depth.

What actually goes wrong on site when the fixing depends on that extra depth?

You only learn where the wall is solid once the bit is in it. Holes set out on paper land where they land — on a bed or head joint, on a web, or through the face shell into a void, and in hollow work the extra depth you scaled the capacity on can end up in air. Hammer action makes it worse: it spalls the shell around the hole and leaves the anchor bearing on a crater instead of sound block, which is why drilling hollow units in rotation only is worth the extra minute. Then the unglamorous ones — a hole left full of drilling dust, since adhesive bonds to whatever it touches; a fixing set too near the end of a block or beside a control joint; a setting torque nobody checked. When the capacity comes up short, the experienced answer is rarely to drill deeper. It is to change the anchor, add fixings so the load spreads over more of the wall at the spacing the manufacturer allows, or have samples pull-tested in that actual wall — with the specifier setting the test load and the margin taken off it, because the load an anchor reaches in a test is not the load it is then designed to carry.

Materials & Quantities

CMU Anchor Embedment Scaling Calculator

Scale a masonry anchor's rated pull-out capacity to a different embedment depth, from its manufacturer's reference test data.

Answers as you typeNo submit button
Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Manufacturer Rated Capacity at Reference Embedment

The anchor's rated capacity at its tested reference embedment depth, from the manufacturer's ICC-ES report.

From the report, and from the RIGHT ROW of it. An evaluation report gives capacities against a specific base material and condition — grouted or hollow, into the face shell or into a bed joint, and often a minimum unit strength — and a value lifted from the wrong row is already wrong before any scaling is applied to it. Match the row to the wall as built, not as drawn.

Reference Embedment Depth

The embedment depth the rated capacity was tested at.

The baseline the scaling works from, which is why it has to be the tested depth rather than the one you intend to use. Scaling away from a tested point is an estimate and not a test result, and capacity does not keep rising with depth indefinitely — past a point the failure stops being the anchor pulling out and starts being the masonry breaking out around it. A large extrapolation is a reason to find a report that covers the depth you actually want.

Actual (Planned) Embedment Depth

The embedment depth you're actually planning to use.

Deeper than the reference embedment does not scale upward here. The rated figure was measured at one depth, and a depth nobody tested has no capacity attached to it — if you are installing deeper, the report's own entry for that depth is the number to use.

Wall Condition at the Anchor

Whether there is solid material behind the face shell where the anchor lands.

A standard block's face shell is about 32 mm (1¼ in). In an ungrouted wall the hole passes into a void beyond it, so drilling deeper adds no bearing — the anchor is held by the face shell and whatever the sleeve or toggle does inside the cell. This page will not convert that into a number, because the rated capacity you enter was itself measured in a particular wall, and applying a face-shell reduction to a figure already measured in hollow block would count it twice. What it will do is tell you when the two do not obviously match, so you go back to the report for the row that fits your wall.

Scaled capacity estimate

1.1 kips

Low confidence

The embedment you entered is deeper than the one the capacity was rated at, so this reports the RATED capacity rather than scaling it up. Linear scaling past a tested depth would be extrapolation, and masonry anchor capacity does not behave linearly there — it flattens off as the failure moves from the anchor into the block. The evaluation report will have a row for the deeper embedment; use that figure, not this one. Establish whether the cell is grouted before relying on this. The same anchor at the same depth carries very different loads in a grouted cell and a hollow one, and the evaluation report tabulates them separately. Linear scaling is a rough approximation, not a substitute for actual manufacturer test data at your specific embedment depth — masonry anchor behavior is governed by the specific product's ICC-ES evaluation report, which should be consulted directly whenever the exact embedment you're using has its own tested/rated value.

Rated capacity entered: 1.12 kips
Embedment ratio applied: 1

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

Masonry anchor capacity is governed by manufacturer ICC-ES evaluation report testing rather than a general calculable formula; a common simplified approximation scales the rated capacity linearly with embedment depth relative to the manufacturer's tested reference embedment
The same approximation does not run the other way: scaling above the tested embedment extrapolates outside the evaluated range, where masonry capacity flattens rather than continuing to rise, so this page holds the result at the rated capacity instead

Inputs used

Manufacturer Rated Capacity at Reference Embedment: 1.12 kip
Reference Embedment Depth: 3 in
Actual (Planned) Embedment Depth: 4 in
Wall Condition at the Anchor: Not established yet

Intermediate steps

Rated capacity entered: 1.12 kips
Embedment ratio applied: 1

Final result1.12 kips

Confidence note: The embedment you entered is deeper than the one the capacity was rated at, so this reports the RATED capacity rather than scaling it up. Linear scaling past a tested depth would be extrapolation, and masonry anchor capacity does not behave linearly there — it flattens off as the failure moves from the anchor into the block. The evaluation report will have a row for the deeper embedment; use that figure, not this one. Establish whether the cell is grouted before relying on this. The same anchor at the same depth carries very different loads in a grouted cell and a hollow one, and the evaluation report tabulates them separately. Linear scaling is a rough approximation, not a substitute for actual manufacturer test data at your specific embedment depth — masonry anchor behavior is governed by the specific product's ICC-ES evaluation report, which should be consulted directly whenever the exact embedment you're using has its own tested/rated value.

What this calculation does not cover

No safety factor is applied, and nothing here knows what basis your rated figure was on. Enter an ultimate test load and you get a scaled ultimate load back; enter an allowable working load and you get a scaled working load. This is not a design capacity and it does not replace the manufacturer's tabulated value for your actual embedment, signed off by whoever is responsible for the connection.
Only the two depths and the rated number reach the arithmetic. Edge distance, spacing between anchors, block and grout strength, mortar joints, cracked masonry and the anchor's own steel capacity are not inputs, so a fixing set near the end of a block or hard against its neighbour returns the same figure as one in the middle of a sound wall.
Tension and shear are scaled identically and a fixing loaded in both at once is not checked against any interaction rule. The page has no input for load direction and cannot tell which one you are asking about.
Scaling down assumes capacity falls in step with depth. Where the failure is a cone breaking out of the block rather than the anchor pulling through, capacity drops off faster than that below the tested depth, so a shallow-embedment answer here can read higher than the anchor will actually reach.
The wall condition you select changes the warnings, not the number: a hollow cell and a grouted one at the same two depths return the same capacity. There is no wall thickness or block size input either, so nothing checks that the embedment fits inside the unit, and nothing accounts for installation — a hole landing in a joint or a web, spalling, dust left in the hole, or setting torque.

Add the equipment this sizes

This result is a specification — 1.1 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

QtyItemPrice each ($)

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 2026-09-03 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations2

Masonry anchor capacity is governed by manufacturer ICC-ES evaluation report testing rather than a general calculable formula; a common simplified approximation scales the rated capacity linearly with embedment depth relative to the manufacturer's tested reference embedment
The same approximation does not run the other way: scaling above the tested embedment extrapolates outside the evaluated range, where masonry capacity flattens rather than continuing to rise, so this page holds the result at the rated capacity instead

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.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Anchoring Into Concrete and Masonryuses this calculator
Every concrete anchor drags a cone of substrate with it — edge distance, spacing and embedment are all arguments about that cone.
Dry-Lining a Solid Wall
Filling a Hollow Wall: ICF Cores and Grouted Block Cells

Called something else where you work? Anchor and fixing — the term in each market, how close the equivalence really is, and the standard that governs it.

How to calculate CMU anchor embedment scaling in 5 steps

Manufacturer Rated Capacity at Reference EmbedmentThe anchor's rated capacity at its tested reference embedment depth, from the manufacturer's ICC-ES report.
Reference Embedment DepthThe embedment depth the rated capacity was tested at.
Actual (Planned) Embedment DepthThe embedment depth you're actually planning to use.
Wall Condition at the AnchorWhether there is solid material behind the face shell where the anchor lands.
Scaled capacity estimateThe tool computes the scaled capacity estimate from those figures and shows the formula, its sources, and a confidence rating alongside it.

Frequently asked questions

Why isn't there a simple universal formula for masonry anchor capacity, unlike concrete?: Because masonry anchor capacity depends heavily on the specific block's material properties, face shell thickness, and whether cells are grouted, unlike concrete, which has the well-established ACI 318 breakout formula. Manufacturers establish rated capacities through actual physical testing (ICC-ES evaluation reports) rather than a general calculable formula.
Is linear scaling with embedment depth accurate?: It's a rough approximation useful for a first estimate — actual capacity-vs-embedment relationships in masonry are often non-linear, especially near the face shell thickness limit, so always check whether the manufacturer publishes rated capacity at your specific embedment depth directly instead of scaling.
What if my embedment is deeper than any tested value?: Never extrapolate beyond the manufacturer's tested range, and this page will not do it for you: enter a depth greater than the rated one and it returns the rated capacity unchanged, with a note saying why. Capacity does not keep rising linearly past the tested depth — it flattens as the failure mode moves out of the anchor and into the block — so the honest answer at an untested depth is the last depth that was tested. Contact the manufacturer, or pick the report row that matches what you are installing.
Does drilling deeper into a hollow block help?: Not by itself. Past the face shell — about 32 mm on a standard unit — the hole is in a void, and depth in air carries nothing. What holds a fixing in an ungrouted cell is the face shell plus whatever the sleeve, toggle or screw geometry does behind it, and that is a property of the product rather than of the depth. If the load matters, grout the cell the anchor lands in, or choose a fixing whose evaluation report rates it for hollow block and use that report's figure directly.
Can I use this figure as the design capacity for a fixing that carries load?: No. The page multiplies your rated number by the ratio of two depths and stops there — no safety factor, no reduction for edge distance or anchor spacing, and no way to tell whether what you typed was an ultimate test load or an already-reduced working load, so the answer comes back on whatever basis you fed in. It also cannot tell tension from shear: it will scale either, and a fixing pulled and sheared at once is checked against the interaction rule the manufacturer publishes, not by scaling one number. That is why every result here is flagged low confidence, however small the change in depth. Use it to decide whether a product is worth looking up properly; once the fixing holds something you would not want to fall, the value that goes on the drawing is the manufacturer's tabulated capacity for your actual embedment, block type and edge distance, accepted by the engineer responsible for the connection.
Which depth goes in the boxes — the anchor length, or the depth I drill?: Neither, unless they happen to coincide. Embedment is the depth into the masonry itself, measured from the face of the block, so anything the anchor crosses on the way in — the bracket or ledger, a packing shim, a render or plaster coat — comes off first, and there is no field here for fixture thickness. Drilled depth is not it either: hole depth is whatever that anchor's installation instructions call for, which for many mechanical anchors is deeper than the embedment so the anchor can seat, and for a bonded anchor is the embedment itself in a hole cleaned out afterwards. Either way it is a different number from the depth the capacity was rated at. The other trap is mixing sources: the capacity and the reference depth have to come from the same row of the same table, because a grouted-cell capacity over a hollow-block reference depth is a ratio between two conditions that were never tested together. The depths the page opens with — 75 mm and 100 mm in metric, 3 in and 4 in in imperial, the imperial pair being the metric one converted and then rounded to the nearest quarter inch, which is why 3 in is not exactly 75 mm — exist to show the arithmetic working, not to suggest a depth.
What actually goes wrong on site when the fixing depends on that extra depth?: You only learn where the wall is solid once the bit is in it. Holes set out on paper land where they land — on a bed or head joint, on a web, or through the face shell into a void, and in hollow work the extra depth you scaled the capacity on can end up in air. Hammer action makes it worse: it spalls the shell around the hole and leaves the anchor bearing on a crater instead of sound block, which is why drilling hollow units in rotation only is worth the extra minute. Then the unglamorous ones — a hole left full of drilling dust, since adhesive bonds to whatever it touches; a fixing set too near the end of a block or beside a control joint; a setting torque nobody checked. When the capacity comes up short, the experienced answer is rarely to drill deeper. It is to change the anchor, add fixings so the load spreads over more of the wall at the spacing the manufacturer allows, or have samples pull-tested in that actual wall — with the specifier setting the test load and the margin taken off it, because the load an anchor reaches in a test is not the load it is then designed to carry.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.