Density Unit Converter

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Density Unit Converter + Material Reference Table & Applications

If you’re working with material specs from different suppliers, you’ll often see density listed in different units—sometimes g/cm³, sometimes lb/in³, and so on. It comes up a lot when you’re checking if your bracket or part is going to overload your actuator, or just double-checking weights before selecting a force rating. This tool lets you swap between the most common density units quickly. There’s a quick material table for reference, and some real-world context for why these conversions come up in actual design work.

What Is Density?

Density tells you how much mass a given volume of material contains. For example, steel packs in a lot more mass than aluminium at the same size—that’s why it feels so much heavier for the same part geometry.

Simple Explanation

Imagine two identical suitcases: one full of books, the other stuffed with pillows. Same volume, different mass—and that’s all density is. Engineers use density to estimate part weights, select materials, and make sure systems aren’t overloaded from excess mass—especially in actuators, motors, and any moving structure.

Material Density Reference 0 9 1 2 3 4 5 6 7 8 Density (g/cm³) 8.96 Copper 7.85 Steel 2.70 Aluminium 1.05 ABS Plastic 1.00 Water ~2.9× denser ρ = mass / volume (kg/m³, g/cm³, lb/ft³)

Density Unit Converter

Material Quick-Fill

Converted Values

kg/m³
1000
g/cm³
1
lb/ft³
62.428
lb/in³
0.03613
oz/in³
0.5780

Material Density Reference Table

Material g/cm³ kg/m³ lb/in³
Steel (mild) 7.85 7850 0.2836
Aluminium 2.70 2700 0.0975
Copper 8.96 8960 0.3237
ABS Plastic 1.05 1050 0.0379
Nylon 1.14 1140 0.0412
Water 1.00 1000 0.0361
Engineering calculation notice

This calculator is intended for education, concept evaluation, and preliminary design. Results are based on the equations and assumptions described on this page, but cannot account for every real-world load case, tolerance, material property, environmental condition, installation detail, safety factor, code, or regulatory requirement. Verify all inputs, assumptions, units, and results independently before selecting components or using the result in a real application. Safety-critical, structural, medical, lifting, transportation, or regulated applications must be reviewed by a qualified engineer.

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🎥 Video — Density Unit Converter

Density Unit Converter

How to Use This Calculator

This tool updates as soon as you type—there’s no “Calculate” button. Here’s a typical workflow:

  1. Type your density value into the box. It starts at 1 g/cm³ (water), but you can put in anything from your datasheet.
  2. Choose the units you have from the dropdown menu—g/cm³, kg/m³, lb/ft³, lb/in³, or oz/in³.
  3. Read each result. You’ll see the conversion in every other major unit, updated live while you type.
  4. Use the quick-fill buttons when you need a standard material like steel or aluminium—no need to look up their densities elsewhere.
  5. Reference the table at the bottom if you want an overview of typical engineering materials and their densities side by side.

Density Unit Formula

To switch density units, the calculation goes through a common base (kg/m³), then out to your target unit. The process is:

Valuetarget = Valueinput × (Factorinput / Factortarget)

Each “factor” gets you to kg/m³ from that unit. You’ll find the main factors just below.

Unit Symbol Factor to kg/m³
Kilogram per cubic metre kg/m³ 1
Gram per cubic centimetre g/cm³ 1000
Pound per cubic foot lb/ft³ 16.0185
Pound per cubic inch lb/in³ 27,679.9
Ounce per cubic inch oz/in³ 1,729.99

Simple Example

Convert 1 g/cm³ (water) to all units

Input: 1 g/cm³

Step 1 — Convert to base unit (kg/m³):
1 × 1000 = 1000 kg/m³

Step 2 — Convert to lb/ft³:
1000 / 16.0185 = 62.43 lb/ft³

Step 3 — Convert to lb/in³:
1000 / 27679.9 = 0.03613 lb/in³

Step 4 — Convert to oz/in³:
1000 / 1729.99 = 0.5780 oz/in³

Practical meaning: Water at 1 g/cm³ is the standard reference you can compare everything against. If a datasheet lists a plastic at 1.05, like ABS, you know it’s just over the density of water without doing any conversion.

Engineering Applications

Steel vs. Aluminium — The Weight Trade-Off

Steel is roughly 2.9 times heavier than aluminium by volume. You’ll see this direct ratio whenever you’re looking at changing materials for a part—bracket, mounting plate, actuator frame, whatever. Swap steel (about 7.85 g/cm³) for aluminium (2.70 g/cm³), and you can take out nearly two-thirds of the weight if you keep stiffness the same by making the aluminium part a bit thicker. Important when your actuator force is fixed—less dead weight means more payload capacity.

For example, a 600 g steel bracket could be swapped for aluminium and come out around 200 g for the same function, as long as you design for aluminium’s lower stiffness (its modulus is about a third of steel’s). This is why actuator mounting and robot arms turn to aluminium so often—it gets you lower mass, and that often lets your motor or actuator do the same job for less effort.

Understanding g/cm³ and kg/L — They're the Same Number

Lots of engineers get caught by this: g/cm³ and kg/L are numerically the same for any material. Water is 1.0 in both. It happens because 1 cm³ equals 1 mL, so 1 g/cm³ = 1000 g/L = 1 kg/L. You can just copy the number over, no calculation needed. Useful when dealing with fluids and checking coolant or oil weights for hydraulic reservoirs or tanks.

That’s why g/cm³ is such a handy unit for quick comparisons. If someone tells you a material’s g/cm³, you can make density estimates in your head. Steel is about 8, aluminium is almost 3, plastics somewhere around 1. It keeps mental math fast.

lb/in³ in North American Material Specs

In North America, lb/in³ is standard. For example, steel is about 0.284 lb/in³. This number looks small, but remember, a cubic inch isn’t much volume. You’ll see lb/in³ on ASTM specs, machine shop data, and US supplier catalogs.

This is handy when your part volume comes from a CAD model in in³—just multiply by the density in lb/in³, and you have the weight in pounds straight away. No conversions required. That streamlines design and checks for actuators or motors.

For actuator selection, this really matters when tallying the weight your actuator has to move. Add up all the part volumes, multiply by their densities (in matching units), and you can figure out total load requirements before a prototype is ever built. You'll be less likely to underspec and have to redo your actuator choice later.

Advanced Example

Actuator Load Calculation — Steel vs. Aluminium Bracket

Suppose you’re looking at a bracket with a volume of 18.5 in³. Here’s how you find the weight for both steel and aluminium brackets so you can size an actuator correctly.

Steel bracket:

Steel density = 7.85 g/cm³
Change to kg/m³: 7.85 × 1000 = 7850 kg/m³
Convert to lb/in³: 7850 / 27679.9 = 0.2836 lb/in³

Weight = 18.5 in³ × 0.2836 lb/in³ = 5.25 lb (2.38 kg)

Aluminium bracket:

Aluminium density = 2.70 g/cm³
Change to kg/m³: 2.70 × 1000 = 2700 kg/m³
Convert to lb/in³: 2700 / 27679.9 = 0.09754 lb/in³

Weight = 18.5 in³ × 0.09754 lb/in³ = 1.80 lb (0.82 kg)

Design interpretation:

Switching to aluminium saves you 3.45 lb per bracket. Multiply by four brackets and you save over 13 lb on the moving structure—enough to step down to a lighter actuator. Often, the higher cost of aluminium per unit weight gets offset by overall system savings: smaller actuator, less power, simpler support structure. It’s not always the right move, but on weight-sensitive builds it’s worth checking this tradeoff early.

Frequently Asked Questions

Are g/cm³ and kg/L really the same number? +

Yes — exactly the same. 1 cm³ = 1 mL, and 1000 mL = 1 L, so 1 g/cm³ = 1000 g/L = 1 kg/L. Water at 1.00 g/cm³ is also 1.00 kg/L. You can use either unit interchangeably without any conversion factor.

Does temperature affect density values? +

Absolutely. Materials expand when heated, so the same mass occupies more volume — lowering density. For metals at typical workshop temperatures (15–40°C), the change is small enough to ignore. For liquids and plastics over wider temperature ranges, it matters. The values in our reference table assume room temperature (around 20°C).

Why do North American specs use lb/in³ instead of kg/m³? +

It's the imperial system in action. Most US machining and manufacturing dimensions use inches, so expressing density in lb/in³ lets engineers multiply volume (in³) by density directly to get weight in pounds. No unit juggling. ASTM standards, material certifications, and supplier datasheets all follow this convention.

Can I use this converter for alloys and composite materials? +

Yes — the unit conversion works for any density value. Just enter the specific density of your alloy or composite from its datasheet. Keep in mind that alloy densities vary with composition. 6061 aluminium (2.70 g/cm³) and 7075 aluminium (2.81 g/cm³) are different enough to affect weight calculations on larger parts.

What's the most common mistake when using density in load calculations? +

Mixing unit systems. People multiply a volume in cubic centimetres by a density in lb/in³ and get nonsense. Always confirm both your volume and density use the same unit system before multiplying. This converter helps you get everything into matching units first.

How does density relate to choosing a linear actuator? +

Density determines part weight, and part weight determines the force your actuator needs. Multiply the volume of every component the actuator moves by its material density, add the payload, and you get the total load. That total load — plus a safety margin — is what drives your actuator force specification. Get the density wrong and you'll undersize your actuator.

When should I use a different approach instead of this converter? +

If you're working with porous materials like foams, sintered metals, or honeycomb structures, the "bulk density" differs significantly from the base material density. You'll need to account for porosity separately. Similarly, for fiber-reinforced composites, use the rule of mixtures rather than a single density value.

About the Author

Robbie Dickson — Chief Engineer & Founder, FIRGELLI Automations

Robbie Dickson brings over two decades of engineering expertise to FIRGELLI Automations. With a distinguished career at Rolls-Royce, BMW, and Ford, he has deep expertise in mechanical systems, actuator technology, and precision engineering.

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