What formula is used to calculate plastic hexagon bar weight?

The formula is: Weight = (√3/2) × AF² × Length × Density. AF (across-flats) and length are converted to meters internally. The cross-section area of a regular hexagon expressed in terms of the across-flats distance AF is (√3/2) × AF² ≈ 0.866 × AF². Multiplying by length gives volume (m³), and multiplying by plastic density (kg/m³) gives weight in kilograms.

What is the across-flats (AF) dimension?

The across-flats (AF) dimension, also called width across flats or wrench size, is the distance between two parallel flat sides of a hexagonal bar. It differs from the across-corners dimension, which equals AF × (2/√3) ≈ AF × 1.155.

What plastic densities does this calculator use?

PVC: 1400 kg/m³, HDPE: 955 kg/m³, LDPE: 920 kg/m³, Nylon (PA6/PA66): 1150 kg/m³, Polypropylene: 905 kg/m³, Polycarbonate: 1200 kg/m³, Acrylic/PMMA: 1180 kg/m³, ABS: 1050 kg/m³, PTFE: 2200 kg/m³. A custom density field is provided for specialty or filled plastics.

Does this calculator support metric and imperial units?

Yes. The across-flats dimension can be entered in mm, cm, or inches. Bar length can be entered in meters, mm, feet, or inches. All values are converted to meters internally before the calculation.

How does plastic hex bar weight compare to a round bar of the same nominal size?

A hexagon bar is heavier than a round bar of the same nominal (AF) diameter. The hexagon cross-section area is (√3/2) × AF² ≈ 0.866 × AF², whereas a round bar area is (π/4) × D² ≈ 0.785 × D². So a hex bar weighs roughly 10% more than a round bar of the same nominal size, for the same material.

Can I calculate the total weight for multiple bars?

Yes. Enter the number of bars in the Quantity field and the calculator will show both the per-bar weight and the total weight for the entire batch.

Plastic Hexagon Bar Weight Calculator

Enter the across-flats size, bar length, and plastic type to instantly calculate plastic hexagon bar weight in kg and lbs.

Bar Dimensions

Across-Flats (AF)

Distance between two parallel flat sides (wrench size).

Bar Length

Plastic Type

Quantity (bars)

Formula Reference

W = (√3/2) × AF² × L × ρ

Where AF = across-flats (m), L = bar length (m), ρ = plastic density (kg/m³), W = weight (kg). Cross-section area = (√3/2) × AF² ≈ 0.866 × AF².

Enter dimensions on the left and click Calculate.

Plastic Type Densities

Plastic	Common Use	kg/m³	lb/in³
PVC	Pipe / Chemical	1400	0.0506
HDPE	Tanks / Cutting boards	955	0.0345
LDPE	Film / Packaging	920	0.0332
Nylon (PA6/PA66)	Gears / Bearings	1150	0.0415
Polypropylene (PP)	Automotive / Lab	905	0.0327
Polycarbonate (PC)	Lenses / Safety	1200	0.0433
Acrylic (PMMA)	Signs / Optics	1180	0.0426
ABS	Enclosures / 3D print	1050	0.0379
PTFE (Teflon)	Seals / Chemical	2200	0.0795

Copied!

Summary

Enter the across-flats size, bar length, and plastic type to instantly calculate plastic hexagon bar weight in kg and lbs.

How it works

Enter the across-flats (AF) dimension of the plastic hexagon bar in millimeters, inches, or centimeters.
Enter the bar length in meters, millimeters, feet, or inches.
Select the plastic type from the dropdown to apply the correct density.
Optionally enter a quantity for multiple bars.
The calculator applies W = (√3/2) × AF² × L × ρ and shows weight in kg and lbs.
Click Copy to save the result to your clipboard.

Use cases

Estimating plastic hex bar stock weight for machining and fabrication projects.
Calculating freight and shipping weight for bulk plastic bar orders.
Comparing plastic types by weight for lightweight component design.
Preparing bill of materials for plastic part manufacturing.
Verifying load limits when storing or handling plastic hex bar stock.
Cost estimation for plastic hex bars priced by weight.
Selecting the right plastic grade to meet weight targets in product design.
Comparing hex bar vs. round bar weight for the same nominal plastic size.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu