How to Calculate Aluminum Weight: The Formula for Plate, Bar, Round, and Tube
By Bilbo Baggins
To calculate the weight of any piece of aluminum, multiply its volume in cubic inches by the density of the alloy in pounds per cubic inch. For 6061 that density is 0.0975, and for 7075 and 7050 it is 0.102. That single formula covers plate, sheet, flat bar, round bar, square bar, hex, and tube. The only thing that changes between shapes is how you compute the volume, and this post gives you each one with a worked example. It also gives you the shortcuts worth memorizing, because most of the time you do not need the full calculation.
In Short
- →Every aluminum weight calculation is the same one line: weight = volume x density. Only the volume formula changes with the shape.
- →Density in the units you want: 6061 is 0.0975 lb per cubic inch, 7075 is 0.102, 7050 is 0.102. Use 0.0975 unless you are on a 7xxx alloy.
- →Plate and flat bar: thickness x width x length x density. Round bar: pi x radius squared x length x density. Tube: outside area minus inside area, times length, times density.
- →Quick shortcuts: 6061 plate is 14.04 lbs per square foot per inch of thickness. 6061 flat bar is thickness x width x 1.17 lbs per foot.
- →The 7xxx alloys run about 4.6 percent heavier than 6061 for identical dimensions, because zinc is denser than aluminum.
- →Weight is what you get billed on and what determines whether your order ships parcel or freight, so it is worth computing before you order.
The Density Numbers
Start here, because everything else is arithmetic. Density varies by alloy because the alloying elements have different densities than aluminum itself. Zinc, the main addition in the 7xxx series, is substantially denser, which is why 7075 and 7050 weigh more than 6061 for identical dimensions.
| Alloy | g/cm3 | lb/in3 | lb/ft3 | kg/m3 |
|---|---|---|---|---|
| 1100 | 2.71 | 0.0979 | 169.2 | 2710 |
| 2024 | 2.78 | 0.1004 | 173.5 | 2780 |
| 5052 | 2.68 | 0.0968 | 167.3 | 2680 |
| 5083 | 2.66 | 0.0961 | 166.1 | 2660 |
| 6061 | 2.70 | 0.0975 | 168.6 | 2700 |
| 6063 | 2.70 | 0.0975 | 168.6 | 2700 |
| 7075 | 2.81 | 0.102 | 175.4 | 2810 |
| 7050 | 2.83 | 0.102 | 176.7 | 2830 |
| Cast tool and jig | 2.80 | 0.101 | 174.8 | 2800 |
Plate, Sheet, and Flat Bar
The simplest case, and the one most orders come down to. A rectangular solid.
Rectangular stock
W = T x Wd x L x D
= A 2 x 12 x 24 inch piece of 6061 = 2 x 12 x 24 x 0.0975 = 56.2 lbs
- W
- weight in pounds
- T
- thickness in inches
- Wd
- width in inches
- L
- length in inches
- D
- density in lb per cubic inch
Round Bar
Round stock uses the area of a circle. The most common mistake here is using the diameter where the formula wants the radius, which produces a number four times too large.
Round bar
W = pi x (Dia / 2)^2 x L x D
= A 2 inch diameter 6061 bar, 36 inches long = 3.1416 x 1 x 36 x 0.0975 = 11.0 lbs
- Dia
- diameter in inches
- L
- length in inches
- D
- density in lb per cubic inch
Square, Hex, and Tube
Three more volume formulas and you have covered essentially everything a distributor stocks.
| Shape | Volume formula | Weight |
|---|---|---|
| Square bar | Side x Side x Length | Volume x density |
| Hex bar | 0.866 x AcrossFlats^2 x Length | Volume x density |
| Round tube | pi x (OD/2)^2 minus pi x (ID/2)^2, times Length | Volume x density |
| Square tube | (OD^2 minus ID^2) x Length | Volume x density |
| Angle | (LegA + LegB minus Thickness) x Thickness x Length | Volume x density |
The Shortcuts Worth Memorizing
In practice you rarely need the full formula. These four cover most of what a buyer or estimator actually asks.
| Question | Shortcut | Example |
|---|---|---|
| 6061 plate, lbs per square foot | 14.04 x thickness in inches | 1.5 in = 21.1 lb/sq ft |
| 7075 or 7050 plate, lbs per square foot | 14.69 x thickness in inches | 1.5 in = 22.0 lb/sq ft |
| 6061 flat bar, lbs per foot | T x W x 1.17 | 1 x 4 in = 4.68 lb/ft |
| 7075 flat bar, lbs per foot | T x W x 1.224 | 1 x 4 in = 4.90 lb/ft |
Three Worked Examples
Real orders, start to finish, so you can check your own arithmetic against something.
- A 1 inch 6061 plate, 18 x 30 inches. Volume = 1 x 18 x 30 = 540 cubic inches. Weight = 540 x 0.0975 = 52.7 lbs. Ships parcel.
- A 4 inch 7075 plate, 12 x 16 inches. Volume = 4 x 12 x 16 = 768 cubic inches. Weight = 768 x 0.102 = 78.3 lbs. Still parcel, but a heavy one.
- A full 60.5 x 144.5 inch mill plate of 2 inch 7075. Volume = 2 x 60.5 x 144.5 = 17,485 cubic inches. Weight = 17,485 x 0.102 = 1,783 lbs. That is a freight shipment and a forklift.
Why the Number Matters Before You Order
Weight is not trivia. It drives three practical decisions and one invoice check.
- Billing. Metal is priced and billed by weight, so computing it tells you what the invoice should say before it arrives.
- Freight mode. Parcel carriers generally top out around 150 lbs per package. Above that you are on LTL freight, which is a different cost structure and a different delivery process.
- Receiving. A 1,783 lb plate needs a forklift and a dock. Knowing that in advance prevents a truck sitting at your door.
- Minimum billed weight. Some suppliers bill a floor regardless of actual weight. Computing the real weight tells you when that floor is quietly inflating a small order.
One formula, volume times density, covers every aluminum shape you will buy. Memorize 0.0975 for 6061 and 0.102 for the 7xxx alloys, memorize 14.04 lbs per square foot per inch for 6061 plate, and you can price and plan almost any order in your head. For anything more complicated, or when you want the number checked, run it through the calculator.
Frequently Asked Questions
What is the formula for aluminum weight?
Weight equals volume times density. For rectangular stock that is thickness x width x length x density. For round bar it is pi x radius squared x length x density. Use 0.0975 lb per cubic inch for 6061 and 0.102 for 7075 and 7050.
How much does 1 inch aluminum plate weigh per square foot?
6061 weighs 14.04 lbs per square foot per inch of thickness, so 1 inch plate is 14.04 lbs per square foot. 7075 and 7050 are 14.69 lbs per square foot per inch, about 4.6 percent heavier.
How do you calculate the weight of aluminum round bar?
Multiply pi by the radius squared to get the cross-sectional area, multiply by length in inches, then multiply by density. A 2 inch diameter 6061 bar 36 inches long is 3.1416 x 1 x 36 x 0.0975, or about 11.0 lbs. Use the radius, not the diameter.
Why does 7075 weigh more than 6061?
7075 contains substantially more zinc, which is denser than aluminum. That puts 7075 at about 2.81 g/cm3 against 6061 at 2.70, roughly 4.6 percent heavier for identical dimensions. On a 2 inch full mill plate that is about 78 lbs of difference.
What is the density of aluminum in pounds per cubic inch?
It depends on the alloy. 6061 and 6063 are 0.0975 lb per cubic inch, 5052 is 0.0968, 2024 is 0.1004, 7075 is about 0.102, and 7050 is about 0.102. Pure aluminum is roughly 0.0979. Use the alloy-specific figure for anything that matters.
Skip the arithmetic
Run your part through the calculator.
Enter alloy, shape, and dimensions and get the weight instantly, then price the same piece cut to size with certs included.