Buyer Guide
Bags getting thinner? Check in 5 minutes
When resin prices rise, some suppliers quietly make bags thinner. With a kitchen scale and simple arithmetic you can prove it yourself.
"The plastic is thinner than my order a few months ago" - comments like this appear in reviews of plastic bags, and more often since plastic prices jumped in March-April 2026. The business daily Kontan (15 April 2026) even reported that plastics producers responded to rising prices by, among other things, reducing product thickness and using more recycled plastic.
The problem is that a thinner bag is hard to notice by hand. The good news: you do not need expensive tools to prove it.
Method 1: weigh 10 sheets
- Keep 10 sheets from every delivery as a dated sample. This is your reference.
- When a new delivery arrives, take 10 sheets of the same size and weigh them on a digital kitchen scale.
- Divide by 10. That is the weight per sheet.
- Compare it with the previous delivery. A difference of 10 percent or more at the same size means the material has changed.
From the weight per sheet you also know how many sheets you get per kilo: 1,000 grams divided by the weight per sheet. If that number jumps while the size stays the same, the bags got thinner.
Method 2: calculate what it should weigh
If the supplier states thickness in millimetres, you can estimate the weight of a flat bag (two layers):
- Weight (grams) = length (cm) x width (cm) x 2 x thickness (mm) / 10 x material density.
- Density is about 0.95 for HDPE, 0.92 for LLDPE and 0.90 for PP.
- Example: a 30 x 50 cm HDPE bag, 0.02 mm thick: 30 x 50 x 2 x 0.002 x 0.95 = about 5.7 grams per sheet.
This is a rough estimate. Gusseted bags weigh more, and carrier bags with cut-out handles weigh less. But if your scale reads far below this figure, the promised thickness deserves a question.
Method 3: measure the thickness directly
A thickness gauge (micrometer) reads down to 0.001 mm. Measure at several points, because thickness that varies within one sheet is also a sign of an uncontrolled process. Specks or uneven colour can indicate recycled content.
Why this is about money, not just quality
Plastic is bought by the kilo. Thinner bags do give more sheets per kilo, but if they tear more often you pay for the wasted ones too. We explain the calculation in Cheap per kilo, expensive per sheet.
Ask for numbers, not adjectives
When you request a quote, ask the supplier to write down the size, the thickness in millimetres and the estimated sheets per kilo. Written numbers can be checked against your scale on every delivery.
Send a sample of the bags you use now to our team. We will weigh it, calculate the sheets per kilo and compare it with the specification we recommend - free, with no obligation to buy. For buyers in Lampung, Palembang, Jambi and Bengkulu, see also our Sumatra service.