What formula is used to calculate plastic square bar weight?

The formula is: Weight = Side² × Length × Density. Side length and bar length are converted to meters, side is squared to get cross-sectional area (m²), multiplied by length for volume (m³), then multiplied by the plastic density (kg/m³) to get weight in kilograms.

What is the density of common engineering plastics?

Densities vary: PVC is about 1380 kg/m³, ABS is 1050 kg/m³, Nylon PA6 is 1130 kg/m³, Polycarbonate is 1200 kg/m³, HDPE is 960 kg/m³, PTFE is 2200 kg/m³, Acetal (POM) is 1410 kg/m³, and PETG is 1270 kg/m³. Use the custom density field if you know your material's exact specification.

Does this calculator support metric and imperial units?

Yes. Side length 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 calculation.

How much lighter is a plastic square bar compared to an aluminum one?

Significantly lighter. Aluminum alloys weigh around 2700 kg/m³, while most engineering plastics range from 960 kg/m³ (HDPE) to 1410 kg/m³ (Acetal). A PVC bar is roughly half the weight of an equivalent aluminum bar, making plastics attractive where weight reduction matters.

Can I calculate total weight for multiple bars?

Yes. Enter the number of bars in the Quantity field and the calculator displays both per-bar weight and total batch weight.

Which plastic should I choose for structural applications?

Nylon (PA6/PA66) and Acetal (POM) offer the best strength-to-weight ratio for structural square bars. Polycarbonate is preferred when impact resistance and transparency matter. HDPE is a good choice for chemical resistance at low cost.

Plastic Square Bar Weight Calculator

Name: Plastic Square Bar Weight Calculator
Availability: InStock
Author: Nham Vu

Enter side width, bar length, and plastic type to instantly calculate the weight of a solid plastic square bar in kg and lbs.

Bar Dimensions

Side Length

Bar Length

Plastic Material

Quantity (bars)

Formula Reference

W = S² × L × ρ

Where S = side length (m), L = bar length (m), ρ = plastic density (kg/m³), W = weight (kg).

Enter dimensions on the left and click Calculate.

Plastic Material Densities

Material	Grade / Application	kg/m³	lb/in³
PVC	Polyvinyl Chloride	1380	0.0499
ABS	Acrylonitrile Butadiene Styrene	1050	0.0379
PA6	Nylon 6 / Polyamide 6	1130	0.0408
PA66	Nylon 66 / Polyamide 66	1140	0.0412
PC	Polycarbonate	1200	0.0433
HDPE	High-Density Polyethylene	960	0.0347
PP	Polypropylene	910	0.0329
PTFE	Teflon / Polytetrafluoroethylene	2200	0.0795
POM	Acetal / Delrin	1410	0.0509
PETG	Polyethylene Terephthalate Glycol	1270	0.0459
PMMA	Acrylic / Plexiglass	1190	0.0430

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Summary

Enter side width, bar length, and plastic type to instantly calculate the weight of a solid plastic square bar in kg and lbs.

How it works

Enter the bar side length in millimeters, centimeters, or inches.
Enter the bar length in meters, millimeters, feet, or inches.
Select the plastic material from the dropdown.
Optionally enter a custom density if your material is not listed.
Enter the quantity for multiple bars.
The calculator applies W = Side² × L × ρ and displays weight in kg and lbs.

Use cases

Estimating plastic material weight for machining and fabrication projects.
Calculating freight and shipping weight for plastic bar stock orders.
Comparing different plastic types to optimize weight and cost.
Preparing bill of materials (BOM) for CNC machining with engineering plastics.
Verifying structural load limits when using plastic square sections.
Cost estimation for plastic bar purchases sold by weight.
Checking whether a plastic bar can replace a metal bar for weight savings.
Material planning for jigs, fixtures, and prototype construction.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu