Short answer
PT, mm, microns, and inches describe thickness. GSM does not.
Points, millimetres, micrometres, and inches are dimensional units, so they can be converted mathematically. In this guide, “pt” means the paper and packaging caliper point of 0.001 inch—not the typographic point used for font size. One caliper point is exactly 0.0254 mm or 25.4 micrometres. GSM means grams per square metre: it describes mass per area, not physical thickness.
That distinction matters in packaging. Two boards with the same GSM can have different density, fiber composition, coating, bulk, moisture, stiffness, and caliper. Two boards with the same caliper can also crease, print, wrap, and carry load differently. Use the converter for unit translation, then specify the real board family, grade, caliper tolerance, surface, structure, and sample acceptance.
Free conversion tool
Paper and packaging board caliper converter.
Enter one dimensional thickness. The results are exact unit conversions, not a GSM estimate or a material recommendation.
Converter boundary: this tool converts one dimensional caliper. It does not convert GSM, predict stiffness, identify a paper grade, account for coating or lamination buildup, select a crease, estimate a finished box dimension, or approve a material.
Three different specifications
Do not collapse mass, thickness, and performance into one number.
Each value answers a different procurement question. A reliable quotation keeps all three attached to the named material and finished structure.
GSM is grams per square metre
GSM describes how much a square metre of material weighs. It can support purchasing and yield calculations, but it does not state the board's thickness, density, bending stiffness, coating, or crease performance.
Caliper is physical thickness
Caliper may be written in pt, mm, micrometres, or inches. It affects panel buildup, cavity size, scores, wrapped corners, lid fit, drawer clearance, and outside dimensions—but still does not describe the complete material.
Performance belongs to the converted pack
Stiffness, fold quality, load response, surface rub, moisture behavior, packing-line performance, and transit protection depend on the actual grade, grain, construction, finish, geometry, manufacturing condition, and test method.
Exact unit chart
Common point-to-mm paper thickness conversions.
The chart converts nominal dimensional caliper only. It does not assign a GSM, grade, coating, stiffness, or packaging use.
Scroll horizontally to view all columns →
| Points | Millimetres | Micrometres | Inches |
|---|---|---|---|
| 8 pt | 0.2032 mm | 203.2 µm | 0.008 in |
| 10 pt | 0.2540 mm | 254.0 µm | 0.010 in |
| 12 pt | 0.3048 mm | 304.8 µm | 0.012 in |
| 14 pt | 0.3556 mm | 355.6 µm | 0.014 in |
| 16 pt | 0.4064 mm | 406.4 µm | 0.016 in |
| 18 pt | 0.4572 mm | 457.2 µm | 0.018 in |
| 20 pt | 0.5080 mm | 508.0 µm | 0.020 in |
| 24 pt | 0.6096 mm | 609.6 µm | 0.024 in |
| 28 pt | 0.7112 mm | 711.2 µm | 0.028 in |
| 32 pt | 0.8128 mm | 812.8 µm | 0.032 in |
| 40 pt | 1.0160 mm | 1,016.0 µm | 0.040 in |
| 60 pt | 1.5240 mm | 1,524.0 µm | 0.060 in |
| 80 pt | 2.0320 mm | 2,032.0 µm | 0.080 in |
| 100 pt | 2.5400 mm | 2,540.0 µm | 0.100 in |
Why GSM is different
A GSM-to-thickness chart needs the actual grade behind it.
A supplier- or mill-specific table can be useful for one defined product family. A universal table is unsafe because bulk and density change across materials.
Scroll horizontally to view all columns →
| Term | What it describes | What still needs confirmation |
|---|---|---|
| GSM | Mass per square metre | Caliper, density, coating, stiffness, grade, moisture, and performance |
| PT / mm / µm | Nominal physical thickness | Material family, tolerance, mass, stiffness, surface, crease, and use |
| SBS / FBB / kraft | Broad paperboard family or market language | Exact mill grade, coated sides, shade, GSM, caliper, fiber statement, and availability |
| Greyboard | Broad rigid-board family | Grade, caliper, tolerance, density or mass, flatness, moisture, surface, and wrap construction |
| Corrugated grade | Combined board construction or performance convention | Flute, liners, medium, total caliper, test method, units, sample condition, and acceptance |
| Laminated board | Multiple layers joined into one stock or component | Each layer, adhesive, compression, total finished caliper, crease route, surface, and delamination risk |
Safe comparison: if two quotations use different board descriptions, ask each supplier to state the exact proposed construction, nominal GSM where relevant, nominal caliper and tolerance, measurement condition, surface, grade reference, and sample route. Do not normalize unlike materials with an assumed GSM-to-mm ratio.
Choose by packaging family
Thickness enters each structure differently.
- Folding cartons
- Caliper works with grade, grain, crease geometry, coating, panel span, closure, product load, and packing line. Review the complete folding carton specification.
- Rigid boxes
- Board thickness changes corner buildup, lid fit, drawer clearance, insert cavity, wrap geometry, weight, and shipping cube. Start with the custom rigid box route.
- Inserts
- Paperboard caliper affects fold, cavity depth, retention, edges, and stacked buildup; foam or molded fiber needs density and geometry rather than a paper conversion. Compare packaging insert structures.
- Corrugated
- Total caliper depends on the combined board and manufacturing condition. Flute, liners, medium, scores, load and agreed tests belong in the shipping-box specification.
Measurement workflow
Define where, when, and how caliper is measured.
A bare incoming sheet, printed and laminated sheet, wrapped board, scored blank, and finished corner are different measurement objects. Name the object in the specification.
- Identify the board family, supplier proposal, finish, and production state
- Agree the nominal caliper, tolerance, instrument, contact area, and pressure
- Condition materials when moisture or climate can change the result
- Measure representative areas away from crushed scores, edges, and local defects
- Record readings with the material lot, sample revision, and approved construction
- Approve fold, fit, load, print, finish, packing, and transit—not caliper alone
Supplier-ready RFQ
Send a controlled material question—not “What GSM should I use?”
The supplier needs the product, structure, process, route, and acceptance criteria before recommending a grade or caliper.
Start with the real load path
Send finished product dimensions, weight, tolerance, orientation, support points, opening, removal, packing method, distribution route, and the intended box, bag, insert, label, or tube construction.
Name the proposed construction
Request material family and grade, GSM where relevant, nominal caliper and tolerance, coating, surface, color, grain or flute, print, lamination, foil, embossing, adhesive, score, and any documentation scope.
Approve the finished behavior
Define the proof and sample route, measurement method, fit and fold checks, visual standards, load or transit test, packing, inspection record, change control, quantity, destination, and target date.
Paper thickness FAQ
Questions buyers ask before selecting packaging board.
The answers keep exact unit conversion separate from material selection and production approval.