Paper GSM Calculator
Weigh a stack of sheets to get its GSM, or work out how much a paper run weighs.
What this tool does
A paper GSM calculator divides the weight of a stack of sheets by the area they cover. Weigh 500 A4 sheets and get 2,500 g: the area is 500 × 0.0625 m² = 31.25 m², so the paper is 2,500 ÷ 31.25 = 80 GSM. The reverse runs the same formula backwards - 120 GSM A4 at 200 sheets weighs 120 × 0.0625 × 200 = 1,500 g.
Turns the weight of a stack of sheets into grams per square metre.
Runs backwards too, giving the weight of a whole paper run from its GSM.
Covers the full A-series from A0 to A10 as well as custom sheet sizes.
Reports area in square metres and square feet, and weight in grams and pounds.
How to use it
- Choose whether you are weighing paper to find GSM or starting from GSM.
- Pick an A-series size, or Custom to enter your own width and height.
- Set how many sheets you are measuring.
- Enter the total weight, or the GSM if you are working backwards.
- Read the GSM, the area and the per-sheet figures, metric and imperial.
Why use this tool
GSM is printed on the ream wrapper and quoted in every paper catalogue, yet it is really just a division: grams divided by square metres. That matters when the number in front of you is a weight rather than a label - a delivery of sheets, a sample book, a stack pulled off the shelf with no packaging left. Weigh it, measure it, divide, and you know exactly what grade of paper you are holding and whether it matches what was invoiced.
Why we built it
We built this paper GSM calculator because the two directions of the question keep coming up. A printer wants to know the GSM of the stock in the machine; a buyer wants to know what a run of 120 GSM stock will weigh on a pallet or cost per kilogram. One formula covers both, and the only real trap is area: A-sizes are defined by halving, so A4 is exactly 0.0625 m², while a custom sheet must be converted to metres before it is multiplied. Pair it with the print cost calculator when paper is being priced, with the banner size calculator when the sheet is large format, and with the length converter to move dimensions between millimetres, centimetres, metres and inches first.
Weight is also the honest test of a paper claim. A stated GSM is a promise about material per area, and a scale does not read brochures.
Who this tool is for
- Print buyers checking the grade of a delivered stock
- Printers confirming what is loaded in the machine
- Packaging designers estimating weight for shipping
- Stationers and craft sellers listing paper by the ream
- Students and researchers weighing samples for a project
How GSM is worked out
The two formulas
| Quantity | Formula | Example |
|---|---|---|
| Sheet area, A-series | A0 is exactly 1 m², halved down the series | A4 = 1 ÷ 16 = 0.0625 m² |
| Sheet area, custom | width × height, both converted to metres | 210 mm × 297 mm = 0.06237 m² |
| Stack area | sheet area × number of sheets | 0.0625 × 500 = 31.25 m² |
| GSM | total weight ÷ total area | 2,500 ÷ 31.25 = 80 GSM |
| Stack weight | GSM × sheet area × sheets | 120 × 0.0625 × 200 = 1,500 g |
Why the A-series area is exact
A0 is defined as one square metre with a width-to-height ratio of the square root of two, and every size below it is half the area of the one above. That makes the areas exact binary fractions: A1 is 0.5 m², A2 is 0.25, A3 is 0.125 and A4 is 0.0625. The millimetre dimensions printed on a ream are rounded for convenience, so multiplying 210 by 297 gives 0.06237 m² and a slightly different answer.
GSM is weight per unit area, not thickness. Two papers of the same GSM can feel completely different if one is coated and the other is not, and the same sheet can vary a little across a press run.
A worked example
Load the sample and the calculator measures a stack of A4 paper. The inputs are these:
| Input | Value |
|---|---|
| Mode | Weigh sheets to find GSM |
| Sheet size | A4 |
| Sheets | 500 |
| Total weight | 2,500 g |
The calculator returns:
- Sheet area: 0.0625 m²
- Total area: 31.25 m² (336.37 ft²)
- Weight per sheet: 5 g
- GSM: 80
- Total weight: 2,500 g (5.51 lb)
Switch the mode to GSM and run the same formula backwards: 120 GSM over 200 A4 sheets needs 120 × 0.0625 × 200 = 1,500 g of paper.
What you enter, and what you get back
| Item | Details |
|---|---|
| Mode | Weigh to GSM, or GSM to stack weight. |
| Sheet size | A0 to A10, or custom width and height in mm, cm or inches. |
| Sheets | How many you are weighing or costing. |
| Weight or GSM | Total weight in g, kg, lb or oz - or the stated GSM. |
| Result | GSM, sheet area, total area in m² and ft², weight per sheet, total weight in g and lb. |
| Copy | The whole summary as plain text. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| GSM comes out lower than expected | The wrapper, band or tray was weighed with the paper. | Weigh the bare sheets, or subtract the packaging first. |
| A figure such as 79.6 instead of a round number | Sheets vary slightly and kitchen scales round. | Round to the nearest standard grade - 70, 80, 100, 120, 160, 200, 250, 300. |
| Custom size gives an odd area | One dimension is still in the previous unit. | Check the unit select matches both width and height. |
| Same GSM, different feel | GSM measures weight, not coating or stiffness. | Compare the finish and caliper as well as the grade. |
Small stacks exaggerate scale error. Ten sheets of A4 weigh about 50 g, so a scale that reads in whole grams can swing the result several GSM; a ream or a few hundred sheets gives a steadier figure.
Assumptions and limitations
- Assumes every sheet is the same size and weight; a mixed stack gives an average.
- A-series areas are the exact ISO values, so they differ slightly from rounded millimetre dimensions.
- GSM says nothing about thickness, stiffness, opacity or finish.
- The result is only as accurate as the scale and the sheet count you enter.
Frequently asked questions
How do I calculate GSM from weight?
Divide the total weight of the sheets by the total area in square metres. A stack of 500 A4 sheets weighing 2,500 g covers 500 × 0.0625 = 31.25 m², so 2,500 ÷ 31.25 gives exactly 80 GSM.
How do I calculate the weight of a paper order from GSM?
Multiply the GSM by the sheet area, then by the number of sheets. 120 GSM A4 is 120 × 0.0625 = 7.5 g per sheet, so 200 sheets weigh 1,500 g - or 1.5 kg.
What is the area of an A4 sheet in square metres?
Exactly 0.0625 m². A0 is defined as 1 m² and each size below it is half the area of the one above, so A4 is one sixteenth of a square metre, regardless of the rounded millimetre dimensions.
What GSM is normal printer paper?
Everyday office paper runs about 70 to 100 GSM, letterhead and premium stock about 100 to 160 GSM, card from 200 to 300 GSM, and the board used for boxes is 300 GSM and heavier.
Does higher GSM mean thicker paper?
Usually, within one paper family it does, because more material per area means more thickness. Across different papers it can mislead: a coated sheet can be thinner but heavier than an uncoated one of the same thickness.
Is the paper GSM calculator free?
Yes, free to use with no account and no upload. The weighing and area arithmetic happen in your browser, and nothing you enter leaves the page.