A reference guide for anyone who needs to understand plastic bag specifications. It covers thickness conversion between gauge and micron, size conversion from inches to millimetres, how to work out how many bags there are in a kilogram, and the differences between HDPE, LDPE and PP.
We put this together because these are the questions we are asked most often before an order is placed. Every figure below is a standard conversion you can verify independently.
How many microns is 100 gauge?
100 gauge equals 25.4 microns, which is 0.0254 mm or 1 mil. The formula: micron = gauge × 0.254, because 1 gauge is 1/100,000 of an inch, and 1 mil equals exactly 25.4 microns.
| Gauge | Micron (µm) | Millimetres | Mil |
|---|---|---|---|
| 50 | 12.70 | 0.0127 | 0.50 |
| 60 | 15.24 | 0.0152 | 0.60 |
| 80 | 20.32 | 0.0203 | 0.80 |
| 100 | 25.40 | 0.0254 | 1.00 |
| 120 | 30.48 | 0.0305 | 1.20 |
| 150 | 38.10 | 0.0381 | 1.50 |
| 180 | 45.72 | 0.0457 | 1.80 |
| 200 | 50.80 | 0.0508 | 2.00 |
| 250 | 63.50 | 0.0635 | 2.50 |
| 300 | 76.20 | 0.0762 | 3.00 |
| 400 | 101.60 | 0.1016 | 4.00 |
| 500 | 127.00 | 0.1270 | 5.00 |
| 600 | 152.40 | 0.1524 | 6.00 |
Suppliers in Malaysia mostly quote in microns. Overseas factories and buyers often use gauge or mil. If you receive a quote in a unit you are not used to, the table above resolves it.
How do I convert bag size from inches to millimetres?
Multiply inches by 25.4 for millimetres, or by 2.54 for centimetres. Example: a 12″ × 15″ bag is 304.8 mm × 381 mm.
| Inches | Millimetres | Centimetres |
|---|---|---|
| 4″ | 101.6 | 10.16 |
| 5″ | 127.0 | 12.70 |
| 6″ | 152.4 | 15.24 |
| 7″ | 177.8 | 17.78 |
| 8″ | 203.2 | 20.32 |
| 9″ | 228.6 | 22.86 |
| 10″ | 254.0 | 25.40 |
| 12″ | 304.8 | 30.48 |
| 14″ | 355.6 | 35.56 |
| 15″ | 381.0 | 38.10 |
| 16″ | 406.4 | 40.64 |
| 18″ | 457.2 | 45.72 |
| 20″ | 508.0 | 50.80 |
| 24″ | 609.6 | 60.96 |
Bag sizes in Malaysia are usually quoted in inches, but technical specifications and print artwork are normally in millimetres.
How many plastic bags are there in 1 kg?
Work out the weight of one piece first, then divide 1,000 grams by that weight.
Weight per piece (g) = Length(cm) × Width(cm) × 2 layers × Thickness(cm) × Density(g/cm³) Thickness(cm) = micron ÷ 10,000 Pieces per kg = 1,000 ÷ weight per piece
Worked example
Flat bag 30 cm × 25 cm, 30 micron, density 0.95 g/cm³ Thickness = 30 ÷ 10,000 = 0.003 cm Weight = 30 × 25 × 2 × 0.003 × 0.95 = 4.27 g per piece Pieces / kg = 1,000 ÷ 4.27 ≈ 234 pieces
Gusseted, handled or side-folded bags use more material than a flat bag of the same outer dimensions. For an exact figure, the actual cut of the bag has to be accounted for.
| Material | Density (g/cm³) |
|---|---|
| HDPE | 0.941 – 0.965 |
| LDPE | 0.910 – 0.925 |
| LLDPE | 0.915 – 0.925 |
| PP / OPP | 0.895 – 0.920 |
What is the difference between HDPE, LDPE and PP?
HDPE is stiff and crinkly. The usual choice for carrier and grocery bags. LDPE is softer and stretchier, suited to courier bags that need to give without tearing. PP and OPP are the clearest and most rigid, chosen when how the product looks inside the bag matters.
| HDPE | LDPE | PP / OPP | |
|---|---|---|---|
| Feel | Stiff, crinkly | Soft, stretchy | Rigid, smooth |
| Clarity | Opaque to translucent | Translucent | Clearest |
| Tear resistance | High for its thickness | Stretches first | Moderate, can crack |
| Flexibility | Low | High | Low |
| Print finish | Good | Good | Sharpest |
| Common use | Carrier, grocery | Courier bags | Product display |
If you already know which material fits your product, our plastic bag supplier page covers sizing, printing and order details. For an eco-conscious HDPE or LDPE option, see our biodegradable plastic bag supplier page.
What thickness do I need for my bags?
There is no single correct thickness. Four things decide it:
- Weight carried. The heavier the contents, the thicker the bag needs to be so the handle does not give way.
- Shape of contents. Items with sharp corners or edges need more thickness than soft items of the same weight.
- How many times it is used. Single-use bags can be thinner. A bag you want customers to keep and reuse needs to be thicker, and that also means your brand stays in view for longer.
- How it is handled. Bags that pass through courier sorting centres take rougher handling than bags handed over at a counter.
If you are not sure, tell us what is going into the bag and how it will be used. That is the information we need to recommend a suitable thickness and material.