Lb to Gsm Calculator

Paper Weight (lb) to GSM Calculator

Bond / Writing / Ledger (17″ x 22″) Text / Book / Offset (25″ x 38″) Cover (20″ x 26″) Index (25.5″ x 30.5″) Tag (24″ x 36″) Bristol (22.5″ x 28.5″)

Calculated Density

Grams per Square Meter (g/m²)

function calculateGSM() { var lbWeight = document.getElementById("basisWeight").value; var multiplier = document.getElementById("paperType").value; var resultContainer = document.getElementById("gsm-result-container"); var display = document.getElementById("gsmResultDisplay"); if (lbWeight === "" || isNaN(lbWeight) || lbWeight <= 0) { alert("Please enter a valid positive number for Basis Weight."); return; } var gsmResult = parseFloat(lbWeight) * parseFloat(multiplier); display.innerHTML = gsmResult.toFixed(2); resultContainer.style.display = "block"; }

Understanding Paper Weight: lb to GSM Conversion

In the printing and paper industry, measuring paper thickness and density can be confusing because different regions use different systems. While most of the world uses GSM (Grams per Square Meter), the United States relies on Basis Weight (measured in pounds or lbs).

The challenge with the "lb" system is that the weight depends on the "Basis Size" of the specific paper category. For example, 20 lb Bond paper is not the same thickness as 20 lb Cover paper. This calculator simplifies the process by applying the correct conversion factors for each paper category.

Common Paper Categories and Their Factors

To convert pounds to GSM, you must know the paper's category. Here are the most common types and how they translate:

• Bond / Writing: Used for office printers and letterheads. Standard size is 17″ x 22″. (Multiplier: 3.76)
• Text / Offset: Used for book pages and flyers. Standard size is 25″ x 38″. (Multiplier: 1.48)
• Cover: Heavy stock used for business cards and book covers. Standard size is 20″ x 26″. (Multiplier: 2.70)
• Index: Stiff, inexpensive cardstock. Standard size is 25.5″ x 30.5″. (Multiplier: 1.81)

The Mathematical Formula

The general formula for converting U.S. Basis Weight to GSM is:

GSM = (Basis Weight × 1406.5) / (Basis Area in Square Inches)

Examples of lb to GSM Conversions

Paper Type	US Weight (lb)	Metric (GSM)
Standard Copy Paper (Bond)	20 lb	75 GSM
Heavy Letterhead (Bond)	24 lb	90 GSM
Magazine Page (Text)	80 lb	118 GSM
Business Card (Cover)	100 lb	270 GSM

Why Convert lb to GSM?

International trade and digital printing standards almost exclusively use GSM. If you are ordering paper from overseas or setting up a high-end digital press, you will likely need the GSM value to ensure the paper weight is compatible with the machine's specifications. Using a higher GSM than recommended can lead to paper jams, while too low a GSM can result in poor ink absorption or transparency issues.