⚡ Key Takeaways & Direct Technical Answer
- Kraft paper weight is specified in GSM (metric) or lb basis weight (US); 1 lb (17×22-500) equals roughly 3.76 GSM.
- Common B2B grades span 40 GSM tissue to 300 GSM heavy-duty kraft for bags, wrapping, interleaving, and void fill.
- Matching weight to application prevents failure: tear strength, burst (Mullen), and stiffness all scale with basis weight.
- Unbleached kraft delivers verified sustainability gains under ISO 14040 lifecycle assessment and supports PPWR/EPR reporting.
Kraft Paper Weight Chart: GSM to LB Basis Weight Guide
kraft paper weight chart – Recycled Kraft Paper and Sustainable Corrugated Board (TadaPack Engineering Guide)
Specifying kraft paper by weight is one of the most common failure points in B2B packaging procurement. A buyer requesting “80 lb kraft” without clarifying basis size, or “100 GSM” without an application context, risks receiving a sheet that tears on the filling line or inflates freight cost per unit. This guide provides the working kraft paper weight chart, the conversion math, and application-matched recommendations used in structural engineering practice. For broader material selection logic, see our pillar hub on Packaging Materials & Processes.
How Kraft Paper Weight Is Measured
Two systems dominate global specification:
GSM (grams per square meter). The ISO-metric standard. A 0.001 m² sample is weighed; grams multiplied by 100 gives GSM. GSM is independent of sheet size, making it the preferred figure for international procurement and for compliance documentation.
US basis weight. Weight in pounds of a ream (500 sheets) cut to a designated basis size. For kraft and other paper grades, the standard basis size is 17 x 22 inches (3.8 ft² per sheet, ~1,892 ft² per ream). Critical caveat: linerboard and corrugated use a different basis (24 x 36 in, 1,000 ft²), so a “26 lb liner” is not equivalent to a 26 lb kraft sheet.
Conversion formula: GSM = basis weight (lb) x 140.5 / 1,000, divided by basis area in ft² per ream / 1,000. For the 17 x 22-500 kraft basis, the practical shortcut is:
1 lb basis weight ≈ 2.708 GSM — or inversely, GSM / 2.708 = lb basis weight. So 100 GSM kraft ≈ 37 lb.
Kraft Paper Weight Chart: Application-Matched Grades
| GSM | US Basis (17×22-500) | Typical Application |
|---|---|---|
| 35–60 GSM | 13–22 lb | Void fill, interleaving, light wrap |
| 70–90 GSM | 26–33 lb | Wrapping, dunnage bags, masking |
| 100–140 GSM | 37–52 lb | Multiwall bags, heavy-duty wrap |
| 150–300 GSM | 55–110 lb | Merchandise bags, covers, sleeves |
Below 35 GSM, treated tissue and machine-glazed grades dominate; above 300 GSM, the product transitions to paperboard (kraft board) rather than paper.
Mechanical Properties That Scale With Weight
Basis weight is a proxy for performance, but engineers should verify the metrics that actually predict field failure:
- Tensile and tear strength scale roughly linearly with GSM in the machine direction (MD); cross-direction (CD) tear is typically 15–30% lower on machine-made kraft.
- Mullen burst on standard unbleached kraft runs roughly 0.4–0.55 kPa per GSM; 100 GSM virgin kraft typically bursts at 350–420 kPa.
- Stiffness scales with the cube of caliper, so a 120 GSM sheet (≈150 µm) is dramatically stiffer than a 60 GSM sheet (≈80 µm) — decisive for bag formation and dispensing.
High wet-strength additives (typically 0.5–1.0% resin) are specified for dunnage and outdoor exposure without altering GSM.
Printing Considerations by Weight
Sheet weight affects ink holdout and rub resistance. Lighter sheets (below 70 GSM) absorb water-borne vehicles faster and can cockle — a key reason to align substrate with fluid chemistry. Our technical guides on Water Based Printing Ink: B2B Specs, Performance & Compliance and Water Based Inks for Printing: B2B Buyer’s Technical Guide cover viscosity, pH, and drying windows matched to uncoated kraft absorbency. On heavy kraft (150+ GSM), surface sizing also matters for flexo line screens above 100 lpi.
Sustainability and 2026 Compliance Reporting
Unbleached kraft remains a compliance-friendly substrate under the EU Packaging and Packaging Waste Regulation (PPWR), which drives recyclability-by-design and recycled-content reporting through 2030, and under US state EPR schemes in California, Oregon, Colorado, and Maine. Weight matters directly: EPR fee modulation is often calculated per tonne of packaging placed on market, so downgauging from 90 to 70 GSM wrap — where burst strength allows — reduces both material cost and eco-modulated fees. Recycled and FSC-certified kraft grades also carry measurably lower cradle-to-gate carbon footprints when evaluated under ISO 14040 Environmental Lifecycle Assessment methodology, which buyers increasingly require as third-party documentation.
Procurement Checklist
- Always state GSM and end application; treat lb specs with the 2.708 conversion only after confirming basis size.
- Require TAPPI-tested MD/CD tensile and burst data, not just nominal weight.
- Request FSC or recycled-content certificates for EPR documentation.
- Pilot-run print fluids on the actual GSM before committing to a grade change.
- Confirm machine-direction orientation for applications where tear initiation matters.
Specifying kraft by application-matched GSM — verified with burst and tear data — eliminates the majority of field failures and keeps packaging within 2026 fee-modulation thresholds.
Frequently Asked Questions (FAQ)
How do I convert kraft paper lb basis weight to GSM?
For standard kraft basis (17 x 22 in, 500-sheet ream), multiply pounds by 2.708 to get GSM. Example: 40 lb kraft ≈ 108 GSM. Always confirm basis size first, since linerboard uses a different basis.
What GSM kraft paper should I use for wrapping vs. bags?
General wrapping performs reliably at 70–90 GSM; heavy-duty wrap and dunnage need 100–140 GSM. Merchandise and multiwall bags typically require 100–300 GSM depending on payload and handling stress.
Does higher GSM kraft paper cost more in EPR or PPWR fees?
Yes. EPR fee modulation is largely weight-based per tonne placed on market, so heavier kraft raises fees. Downgauging GSM where burst and tear performance still meet spec cuts both material and compliance costs.
Engineering Your Next High-Performance Packaging Batch
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