What is the weight of a 36 mm foundation bolt 1200 mm long?

About 9.59 kg. A 36 mm round bar weighs roughly 7.99 kg per metre, so 1.2 m comes to 9.59 kg. Base plate, gussets, pipe sleeve or tuck nut are added on top.

Is the threaded length of a foundation bolt weighed at full diameter?

In normal trade practice yes. The whole length is billed at nominal diameter. Weighing the threaded portion at core diameter gives a lighter figure that will not match the customer's own calculation.

What is a tuck nut on a foundation bolt?

A nut welded low on the rod below the base plate to key the bolt into the concrete. It is bored oversize rather than threaded so it slides onto the rod before welding, often one size larger than the rod.

How is a triangular stiffener gusset weighed?

As half a rectangle: base times height divided by two, multiplied by thickness and by 7.85 g/cm3, then by the number of gussets. Weld metal is extra.

Foundation & Anchor Bolt Weight Calculator

Weight of straight foundation bolts and welded plate anchor assemblies — rod, base plate, gussets, pipe sleeve and tuck nut, itemised and totalled for the lot. Built the way we quote them, by a manufacturer who makes them.

The bolt

Diameter

Total length incl. thread, mm

Thread, top end, mm

Thread, bottom end, mm

Base plate

Shape

Length, mm

Width, mm

Thickness, mm

Stiffener gussets

Base, mm

Height, mm

Thickness, mm

Number off

Triangular gussets, calculated as half of base × height × thickness.

Pipe sleeve

Nominal bore

Class

Pipe length, mm

Resolves to

Tuck nut (welded, bored)

Nut size

Across flats, mm

Thickness, mm

Bore, mm

Enter 0 for an end with no thread. Nut size defaults one size above the rod, bore to rod diameter plus 1 mm. Both are editable — practice varies by customer. Across-flats and thickness above M64 follow DIN 934; check them against the nut you are actually welding, since nuts that size are often made to drawing.

Quantity

Number of bolts

9.59 kg each

959 kg for 100 pieces

How foundation bolt weight is calculated

A foundation bolt is a round bar with a thread on it, so the weight of the bolt itself is the weight of the bar. For a plain round section:

kg per metre = d² × π / 4 × 7.85 ÷ 1000

which is the familiar Indian shop rule d² ÷ 162. A 36 mm bar runs about 8 kg per metre.

Worked example: 36 × 1200, threaded 150 mm each end

Total length 1200 mm, so 900 mm plain and 300 mm threaded
36 mm bar at 7.99 kg/m
Weight = 1.200 m × 7.99 = 9.59 kg

Note that the whole length is taken at 36 mm including the threaded portion. That is deliberate, and it is what the trade bills on. If you weighed the threaded length at its core diameter instead, that 300 mm section would come out roughly a quarter lighter, and your figure would then disagree with the customer’s own calculation. The calculator shows the thread-adjusted figure underneath so you can see the difference, but the headline number is the nominal one.

Large diameter anchor bolts

Anchor bolt diameters have grown with the structures they hold down. Wind turbine bases, tall stacks, heavy press foundations and large equipment skids now routinely call for 90, 100 and 110 mm bolts, sizes that used to be rare. The arithmetic does not change, but the numbers get heavy fast: a 110 mm bar runs about 74.7 kg per metre, so a single 2 m bolt is roughly 150 kg before any plate, gusset or sleeve is welded on. At those sizes the weight calculation stops being a formality and starts driving freight, handling and crane planning.

Unequal thread lengths

Thread lengths are often different at the two ends — 500 mm projecting above the foundation for levelling nuts and adjustment, 100 mm at the embedded end for a nut and washer. Enter each end separately, and put 0 against an end with no thread at all.

Two ways to state the length

Drawings state foundation bolts both ways, and getting them confused is the most common costing error on this product:

Length including thread — 1200 overall, of which 150 each end is threaded, leaving 900 plain
Length excluding thread — 900 rod, with 150 added at each end, giving 1200 overall

Same bolt, two descriptions. The calculator takes either and shows the resulting overall length, so a wrong entry is obvious at once.

Welded plate assemblies

A welded plate anchor bolt is a straight bolt with a base plate welded near the embedded end, which spreads the pull-out load into the concrete instead of relying on a bend. Around it, four items appear on drawings again and again:

Base plate — rectangular or circular, welded square to the rod. Weight is simply length × width × thickness × 7.85.
Stiffener gussets — triangular plates welded to both the base plate and the rod, usually three or four around it, to stop the plate bending away from the rod under load.
Pipe sleeve — a length of pipe welded at mid-section just below the thread, sitting on a small plate. It lets the bolt be adjusted or grouted rather than cast rigid, and protects the thread during the pour.
Tuck nut — a nut welded low on the rod below the plate, giving a mechanical key into the concrete in addition to the plate. It is not a threaded nut doing a threaded job: it is bored oversize so it slides onto the rod, positioned, and welded. Customers commonly call up a nut one size above the rod, so a 32 mm bolt takes a 36-size nut bored around 33 mm.

Because the tuck nut is bored rather than tapped, its weight is not the weight from a standard nut table. The calculator works it as a hexagonal prism less the bore, which is what it physically is.

Round bar weight reference

Plain mild steel round bar at 7.85 g/cm³.

Diameter, mm	kg per metre	kg per 500 mm	kg per 1.5 m
12	0.888	0.44	1.33
16	1.578	0.79	2.37
20	2.466	1.23	3.70
24	3.551	1.78	5.33
27	4.495	2.25	6.74
30	5.549	2.77	8.32
32	6.313	3.16	9.47
36	7.990	4.00	11.99
39	9.378	4.69	14.07
42	10.876	5.44	16.31
45	12.485	6.24	18.73
48	14.205	7.10	21.31
52	16.671	8.34	25.01
56	19.335	9.67	29.00
60	22.195	11.10	33.29
64	25.253	12.63	37.88
68	28.509	14.25	42.76
72	31.961	15.98	47.94
76	35.611	17.81	53.42
80	39.458	19.73	59.19
85	44.545	22.27	66.82
90	49.940	24.97	74.91
100	61.654	30.83	92.48
110	74.601	37.30	111.90

What a foundation bolt drawing should state

Most of the delay in quoting anchor bolts comes from drawings that leave something out. A complete enquiry gives us:

Diameter, total length, and whether that length includes the thread
Thread length at each end separately, since the two are often different
Thread standard — metric coarse, UNC, BSW — and the class or fit required
Material grade or property class, and whether test certificates are needed
Plate size and thickness, gusset size and number off
Pipe size by nominal bore and class, and its length and position on the rod
Tuck nut size and bore, if used
Finish — black, hot-dip galvanised, or painted — and whether nuts and washers are supplied loose with the bolts
Quantity, and the number of nuts and washers per bolt

We manufacture foundation and anchor bolts

Straight, L, J and welded plate types from small sizes up to ø110 mm, in mild steel and in property classes 4.6 through 10.9, with rolled threads up to ø100 mm. Made to your drawing, black or hot-dip galvanised, with nuts and washers to match. S.R. Forgings, Focal Point, Ludhiana, since 2009.

Send your drawing

Common questions

What is the weight of a 36 mm foundation bolt 1200 mm long?: About 9.59 kg. A 36 mm round bar weighs roughly 7.99 kg per metre, so 1.2 m comes to 9.59 kg. Any base plate, gussets, pipe or tuck nut are added on top of that.
Is the threaded length weighed at full diameter?: In normal trade practice, yes. The thread is cut or rolled into the bar and the whole length is billed at nominal diameter. Weighing the threaded portion at core diameter gives a lighter figure that will not match your customer’s own calculation, so it is shown separately rather than used as the headline number.
How is a triangular stiffener gusset weighed?: As half a rectangle: base × height ÷ 2, multiplied by thickness and by 7.85 g/cm³. Multiply by the number of gussets. Weld metal is not included and adds a little on top.
What is a tuck nut on a foundation bolt?: A nut welded low on the rod, below the base plate, to key the bolt into the concrete. It is bored oversize rather than threaded, so it slides onto the rod before welding. Customers often specify a nut one size larger than the rod, for example a 36-size nut bored to about 33 mm on a 32 mm bolt.
Why does the calculated weight differ from the weighbridge?: Calculated weight uses nominal dimensions. Real assemblies carry weld metal, plate is cut and rolled to tolerance, pipe wall varies, and the thread removes or displaces material. On a welded assembly a variation of about five per cent either way is normal, which is why the assembly figure is marked as an estimate.