To calculate weight of coil by lineal feet is a fundamental process in the manufacturing, logistics, and metalworking industries. It involves determining the total mass of a rolled metal strip based on its unrolled length, width, thickness, and material density. Unlike calculating by outer diameter (OD), calculating by lineal feet provides an exact weight based on the known quantity of material length, which is critical for inventory management and production planning.
Purchasing managers, warehouse foremen, and machine operators often use this calculation to verify that delivered coils match the ordered specifications or to determine if a partial coil remaining on a machine has enough footage to complete a production run. Accurate weight calculation prevents overloading transport vehicles and ensures machinery weight limits are respected.
Coil Weight Formula and Mathematical Explanation
The math behind how to calculate weight of coil by lineal feet is based on volume and density. The objective is to first find the total volume of the metal strip in cubic inches, and then multiply that volume by the specific density of the material.
Here is a breakdown of the variables used in the calculation:
Table 1: Variables for Coil Weight Calculation
Variable
Meaning
Unit
Typical Range
Length (L)
Total unrolled length of coil
Lineal Feet (ft)
1,000 – 20,000+
Width (W)
Width of the strip
Inches (in)
1″ – 72″
Thickness (T)
Gauge of the material
Decimal Inches (in)
0.005″ – 0.500″
Density (D)
Weight per unit volume
lbs per cubic inch
0.098 – 0.324
12
Conversion factor
in/ft
Constant
Practical Examples (Real-World Use Cases)
Below are two examples illustrating how to manually calculate weight of coil by lineal feet in different industrial scenarios.
Example 1: Standard Steel Coil for Stamping
A stamping plant has a partial coil of Carbon Steel (Density 0.2833). They measure the footage counter which reads 2,500 lineal feet. The coil is 48 inches wide and has a thickness of 0.060 inches.
Calculation: 2,500 ft × 12 (in/ft) × 48 in × 0.060 in × 0.2833 lbs/in³
Volume Step: 30,000 in (length) × 48 in × 0.060 in = 86,400 in³
Weight Step: 86,400 in³ × 0.2833 = 24,477.12 lbs
Interpretation: The crane must be rated for at least 12.5 tons to move this coil safely.
Example 2: Aluminum Coil for Siding
A supplier is shipping Aluminum coil (Density 0.098). The order is for 5,000 lineal feet, with a width of 24 inches and a thickness of 0.019 inches.
Calculation: 5,000 ft × 12 × 24 in × 0.019 in × 0.098 lbs/in³
Volume Step: 60,000 in × 24 in × 0.019 in = 27,360 in³
Weight Step: 27,360 in³ × 0.098 = 2,681.28 lbs
Interpretation: This weight allows for multiple coils to be loaded onto a standard flatbed truck without exceeding axle limits.
How to Use This Calculator
Select Material: Choose the metal type from the dropdown. This automatically sets the standard density (e.g., Steel at 0.2833). Select "Custom" if you are using an alloy with a specific density not listed.
Enter Length: Input the total lineal feet of the coil. This is often found on the coil tag or production run sheet.
Enter Width: Input the exact width of the strip in inches.
Enter Thickness: Input the material thickness in decimal inches. If you only know the gauge number, consult a gauge chart to convert it to decimals first.
Review Results: The tool will instantly calculate weight of coil by lineal feet, displaying the total weight in pounds, the weight per foot, and the metric equivalent in kilograms.
Key Factors That Affect Coil Weight Results
When you calculate weight of coil by lineal feet, several real-world factors can influence the final accuracy and financial implications.
Material Density Variations: Not all steel is exactly 0.2833 lbs/in³. Alloys with high carbon or other elements may vary slightly. Stainless steel (300 series) is denser (0.290), affecting shipping costs significantly over large volumes.
Crown and Gauge Tolerance: Steel is rarely perfectly flat. "Crown" refers to the center being thicker than the edges. Since calculators assume nominal thickness, actual weight might be 1-2% higher if the material is on the heavy side of the tolerance.
Packaging Weight: The calculated weight is "Net Weight." Skids, spacers, paper wrapping, and strapping (Gross Weight) can add 50-150 lbs per coil, which matters for freight calculations.
Scrap Factor: When purchasing based on weight to produce a specific number of feet, always account for head and tail scrap. You may need to buy 5% more weight than the theoretical calculation suggests.
Telescoping: While this doesn't change weight, loose winding or telescoping increases the volume the coil takes up, potentially impacting shipping space even if the weight calculation is accurate.
Inventory Valuation: In accounting, metal is often valued by weight. An error in the lineal footage input when conducting inventory audits can lead to significant financial discrepancies in the balance sheet.
Frequently Asked Questions (FAQ)
Why is calculating by lineal feet more accurate than by diameter?
Calculating by diameter relies on the assumption that the coil is wound perfectly tight (solid density). If there are air gaps between layers, the diameter method overestimates weight. Lineal feet calculation is based on the actual volume of metal present.
How do I convert Gauge number to Thickness?
Gauge systems vary by material (e.g., 16 gauge steel is different from 16 gauge aluminum). You must use a standard Manufacturer's Standard Gauge (MSG) chart to find the decimal equivalent before using this calculator.
Does this calculator apply to slit coils?
Yes. As long as you input the specific width of the slit strip (mult), the formula remains exactly the same.
Can I calculate the weight of a painted coil?
Paint adds thickness but very little weight compared to steel. For most logistical purposes, use the base metal thickness for the weight calculation to avoid overestimating.
What if my coil is Metric?
If your inputs are in millimeters and meters, you should convert them first: divide mm by 25.4 to get inches, and multiply meters by 3.28084 to get feet.
How does density affect the cost?
Metals are priced per pound or hundredweight (CWT). If you switch from Aluminum to Steel for the same part geometry, the part will be nearly 3x heavier, tripling material costs even if the volume is identical.
Is paper interleave included in the weight?
No. Paper interleave adds spacing but negligible weight. However, it increases the Outer Diameter (OD) significantly.
What is the standard density for Galvanized Steel?
Galvanized steel is generally calculated using the same density as carbon steel (0.2833 lbs/in³) because the zinc coating is very thin, though technically zinc is slightly lighter than iron.
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