{
    "name": "Paper GSM Calculator",
    "url": "https://calculators.geekmidst.com/calculators/paper-gsm-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/paper-gsm-calculator.md",
    "category": "Manufacturing & packaging",
    "description": "Convert GSM into sheet weight, ream weight and total weight for any sheet size, plus the US basis weight in pounds for bond, text, cover or index paper.",
    "summary": "GSM is grams per square metre, so a sheet weighs its area in m² times its GSM. US basis weight is the weight in pounds of 500 sheets of that grade’s basis size.",
    "also_called": [
        "Paper weight calculator",
        "GSM to pounds converter"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "gsm",
            "label": "Paper grammage",
            "type": "number",
            "default": "80",
            "unit": "g/m²"
        },
        {
            "name": "width",
            "label": "Sheet width",
            "type": "number",
            "default": "210",
            "unit": "mm"
        },
        {
            "name": "length",
            "label": "Sheet length",
            "type": "number",
            "default": "297",
            "unit": "mm"
        },
        {
            "name": "sheets",
            "label": "Number of sheets",
            "type": "number",
            "default": "500"
        },
        {
            "name": "grade",
            "label": "US basis grade",
            "type": "select",
            "default": "text",
            "options": {
                "bond": "Bond / writing (17 × 22 in)",
                "text": "Text / book / offset (25 × 38 in)",
                "cover": "Cover (20 × 26 in)",
                "index": "Index (25.5 × 30.5 in)"
            }
        }
    ],
    "outputs": [
        {
            "key": "total_kg",
            "label": "Total weight",
            "format": "number"
        },
        {
            "key": "sheet_g",
            "label": "Weight per sheet",
            "format": "number"
        },
        {
            "key": "ream_kg",
            "label": "Weight per 500 sheets",
            "format": "number"
        },
        {
            "key": "basis_lb",
            "label": "US basis weight",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Sheet (g) = Width (m) × Length (m) × GSM;  Basis (lb) = GSM × Basis area (m²) × 500 ÷ 453.59237",
        "variables": {
            "Basis area": "the grade’s basis sheet in square inches × 0.00064516 m²/in²",
            "453.59237": "grams per pound (exact)"
        }
    },
    "worked_example": {
        "inputs": {
            "gsm": "80",
            "width": "210",
            "length": "297",
            "sheets": "500",
            "grade": "text"
        },
        "steps": [
            "A4 area = 0.21 × 0.297 = 0.06237 m²; × 80 = 4.99 g per sheet.",
            "500 sheets = 2.495 kg.",
            "Text basis 25 × 38 in = 0.6129 m²; 80 × 0.6129 × 500 ÷ 453.59 = 54.0 lb."
        ],
        "result": "A ream of 80 GSM A4 weighs about 2.5 kg, and 80 GSM equals about 54 lb text weight."
    },
    "interpretation": "Pound weights only compare within the same grade: 80 GSM is about 21 lb bond but 54 lb text. GSM compares across all grades.",
    "assumptions": [
        "Basis weights use the standard US basis sheet sizes listed."
    ],
    "limitations": [
        "Actual grammage varies within the mill’s tolerance, and moisture changes weight slightly."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why is 20 lb bond lighter than 50 lb text?",
            "answer": "They use different basis sheet sizes. 20 lb bond is about 75 GSM; 50 lb text is about 74 GSM, so they are almost the same paper."
        },
        {
            "question": "How do I find GSM from a sheet’s weight?",
            "answer": "Divide the weight in grams by the sheet area in m²."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Carton Board Weight Calculator",
            "url": "https://calculators.geekmidst.com/calculators/carton-board-weight-calculator"
        },
        {
            "name": "Printing Ink Consumption Calculator",
            "url": "https://calculators.geekmidst.com/calculators/printing-ink-consumption-calculator"
        },
        {
            "name": "Box Burst Strength Estimate Calculator",
            "url": "https://calculators.geekmidst.com/calculators/box-burst-strength-calculator"
        },
        {
            "name": "Fabric GSM Calculator",
            "url": "https://calculators.geekmidst.com/calculators/fabric-gsm-calculator"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}