Fastener Weight Calculator: Bolts, Nuts, Washers, Rods in kg

This nut bolt weight calculator gives the weight of hex bolts, hex nuts, plain and spring washers, threaded rods, J bolts, L bolts and U bolts in grams and kg. Choose the product and size, then type the length and quantity. Add each item to a list and send it to us on WhatsApp for a quote.

How the Weight Is Worked Out

The calculator finds the volume of steel in each part from its standard sizes and multiplies it by the density. Our hex bolt weight chart uses the same method, so both give the same figures. Sizes are in mm and π/4 = 0.7854.

• Hex bolt: head 0.866 × s² × k, where s is the width across flats and k the head height (ISO 4017 and 4014, or DIN 933 and 931). The thread is a round bar of the pitch diameter d2 = d − 0.6495 × P, where P is the pitch. Any plain shank is a bar of the full diameter d. Half thread bolts take the ISO 4014 thread length (2d + 6 mm up to 125 mm long) unless you type your own.
• Hex nut: (0.866 × s² − 0.7854 × d2²) × m, with the height m from ISO 4032 or DIN 934.
• Plain washer: 0.7854 × (D² − d1²) × h, with outside diameter D, hole d1 and thickness h, sizes to ISO 7089 and DIN 125-A.
• Spring washer: π × (d1 + b) × b × t, with hole d1, section width b and thickness t, sizes to DIN 127 B.
• Threaded rod or stud: 0.7854 × d2² × length. A 1000 mm length gives the threaded rod weight per metre, as in DIN 975.
• J bolt and L bolt: bar length = total length + hook (or leg) length − d, as both are outside sizes. This counts the bend as a sharp corner, so bolts with rounded bends weigh a few percent less. The plain part is at d and the thread at d2.
• U bolt: bar length = 2 × (H − OD ÷ 2) + π × (OD + d) ÷ 2. H is the inside height, from the inside of the bend to the leg end, and OD the pipe outside diameter.

Mild steel and high tensile steel are both 7.85 g/cm³. SS 304 is 7.93 g/cm³, SS 316 is 8.00 g/cm³ and SS 202 about 7.8 g/cm³. For hot dip galvanized parts the calculator adds a 50 micron zinc coat, the minimum batch average in ISO 10684. BSW sizes use BS 1083 heads and nuts. Black BSW bolts with bigger heads weigh more. The calculator lists washers in metric sizes only.

Real parts weigh a little less, because chamfers, thread run-out and tolerances take some steel away. Short bolts of M6 and below can be up to about 15 % lighter.

Worked Example: M12 x 50 Hex Bolt

A fully threaded M12 x 50 hex bolt to ISO 4017, in steel:

• Head: 0.866 × 18² × 7.5 = 2,104 mm³
• Pitch diameter: d2 = 12 − 0.6495 × 1.75 = 10.863 mm
• Threaded shank: 0.7854 × 10.863² × 50 = 4,634 mm³
• Weight: (2,104 + 4,634) × 7.85 ÷ 1000 = 52.9 g

That is 5.29 kg per 100 pieces and about 19 pieces per kg. With a DIN 933 head (19 mm across flats) it weighs 54.8 g, in SS 304 53.4 g and hot dip galvanized about 54.3 g.

J Bolt Weight: M20 Foundation Bolt Example

An M20 J bolt with a 600 mm total length, a 150 mm hook and 100 mm of thread, in mild steel:

• Bar length: 600 + 150 − 20 = 730 mm, with 630 mm plain and 100 mm threaded
• Plain part: 0.7854 × 20² × 630 = 197,920 mm³
• Threaded part: d2 = 20 − 0.6495 × 2.5 = 18.376 mm, so 0.7854 × 18.376² × 100 = 26,522 mm³
• Weight: (197,920 + 26,522) × 7.85 ÷ 1000 = 1,762 g, or about 1.76 kg

Fifty of these weigh about 88.1 kg. Add nuts and washers as separate lines: an M20 hex nut is about 72.7 g and an M20 plain washer 17.2 g.

Pieces per kg: How Many Nut Bolts in 1 kg?

Pieces per kg = 1000 ÷ the weight of one piece in grams. Some examples in steel, with ISO 4032 nuts:

• M8 x 40 hex bolt with nut: 24.5 g a set, about 41 sets per kg
• M10 x 50 hex bolt with nut: 46.7 g a set, about 21 sets per kg
• M12 x 50 hex bolt with nut: 68.8 g a set, about 15 sets per kg, or 13 sets with a plain washer
• Washer weight: an M10 plain washer is 3.57 g, about 280 per kg, and an M12 spring washer 4.0 g, about 250 per kg

To count a large lot, divide its weight by the weight of 100 pieces and multiply by 100.

Bolts, Nuts, Washers and Rods from JMIKS Fasteners

JMIKS Fasteners supplies hex bolts and hex nuts in SS 304, SS 316 and SS 202 and in mild steel and high tensile grades from 4.6 to 12.9. Sizes run from M3 to M36 and 1/4″ to 1-1/4″ BSW. We also supply SS plain washers, spring washers, GI threaded rods, studs, J bolts, L bolts and U bolts. See the hex bolt weight chart for kg per 100 pieces from M6 to M24, and the foundation bolts guide, thread pitch chart and bolt grade chart. For J and L bolt weight per metre, see the foundation bolt weight chart. For head heights and clearance holes, see hex bolt dimensions.

Fastener Weight Calculator FAQs

How many nut bolts are there in 1 kg?

In steel, 1 kg holds about 41 sets of M8 x 40 bolts with nuts, 21 sets of M10 x 50 and 15 sets of M12 x 50. For other sizes, add the bolt and nut weights from the calculator and divide 1000 by the total in grams.

How does the calculator work out J bolt and L bolt weight?

It takes the bar length as the total length plus the hook or leg length, less one bar diameter. That counts the bend as a sharp corner, so a rounded bend uses a little less bar. It then multiplies the plain length by 0.7854 × d² and the threaded length by 0.7854 × d2², adds them and multiplies by 7.85 ÷ 1000 to get grams.

What is the weight of a threaded rod per metre?

In steel, about 0.50 kg for M10, 0.73 kg for M12, 1.33 kg for M16, 2.08 kg for M20 and 3.00 kg for M24, in line with DIN 975.

Does the grade or finish change the weight?

The grade does not: 4.6, 5.6, 8.8, 10.9 and 12.9 steel parts of the same size weigh the same. The material and finish do. A 1 metre M20 threaded rod weighs 2.08 kg in steel, 2.10 kg in SS 304, 2.12 kg in SS 316 and about 2.12 kg hot dip galvanized. Zinc plating adds under 1 %, so the calculator leaves it out.

Why does my weighed part not match the calculator?

The calculator leaves out chamfers and tolerances, so real parts weigh a little less: often 1 to 5 % for bolts and spring washers and up to about 10 % for nuts. DIN 933 heads in M10, M12, M14 and M22 also differ from ISO 4017 heads, so pick the standard that matches your parts.

Get a Quote for Bolts, Nuts and Washers

JMIKS Fasteners is a fastener wholesaler and supplier in Nava Odhav, Ahmedabad. Send the size, length, grade, finish and quantity on WhatsApp (+91 90333 11425) or through the enquiry form, or get our catalogue from the catalogue page. We reply within one working day.