# Paper GSM Calculator

> 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.

Category: Manufacturing & packaging · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/paper-gsm-calculator

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.

## Inputs
- Paper grammage (unit g/m²; default 80)
- Sheet width (unit mm; default 210)
- Sheet length (unit mm; default 297)
- Number of sheets (default 500)
- US basis grade (options: Bond / writing (17 × 22 in), Text / book / offset (25 × 38 in), Cover (20 × 26 in), Index (25.5 × 30.5 in); default text)

## Results
- Total weight
- Weight per sheet
- Weight per 500 sheets
- US basis weight

## Formula

```
Sheet (g) = Width (m) × Length (m) × GSM;  Basis (lb) = GSM × Basis area (m²) × 500 ÷ 453.59237
```

Where:
- Basis area: the grade’s basis sheet in square inches × 0.00064516 m²/in²
- 453.59237: grams per pound (exact)

## Worked example
1. A4 area = 0.21 × 0.297 = 0.06237 m²; × 80 = 4.99 g per sheet.
2. 500 sheets = 2.495 kg.
3. 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.

## What the result means

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 and limits
- Basis weights use the standard US basis sheet sizes listed.
- Actual grammage varies within the mill’s tolerance, and moisture changes weight slightly.

## Questions

### Why is 20 lb bond lighter than 50 lb text?

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.

### How do I find GSM from a sheet’s weight?

Divide the weight in grams by the sheet area in m².

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/paper-gsm-calculator