Paper terms explained by a commercial printer
Index and cover are different paper categories. Neither is automatically better, and their pound ratings cannot be compared directly.
Different categories. Different characteristics.
The better choice depends on the stiffness, surface, weight, durability, and writing experience your project needs.
Index stock is commonly selected for index cards, tabs, dividers, records, and systems that are handled, sorted, filed, or referenced repeatedly. The index-stock weights used in our product line are 90 lb, 110 lb, and 140 lb.
It is available in multiple weights and finishes, so the word “index” alone does not tell you exactly how thick or smooth a finished card will feel.
Cover stock is commonly used for book covers, postcards, invitations, presentation pieces, greeting cards, and other applications that benefit from a substantial surface.
Depending on the specific sheet, it may feel smoother, denser, softer, or more refined than index stock at a similar GSM.
The source of most confusion
In the United States, basis weight is the weight of 500 sheets of paper at a specified basis size. The basis size changes with the paper category.
That means pound ratings are not based on one universal sheet size. For example, a 110 lb index sheet and a 100 lb cover sheet are weighed using different starting dimensions. The higher pound number does not necessarily identify the heavier finished paper.
Practical rule: Never decide that two papers are equivalent merely because the pound numbers match. Identify the paper category and compare GSM before considering thickness, finish, and stiffness.
Technical reference: Case Paper Basis Weight Calculator and Explanation
Real examples from our card production
These Debra Dale Designs stocks show why the category, GSM, and finish are more useful together than a pound rating by itself.
A lightweight, flexible value card suited to large quantities, compact storage, and practice material that may be replaced often.
A substantial everyday index card that balances durability, portability, storage space, and cost.
A firmer premium card with an ultra-smooth writing surface for frequent handling, shuffling, and longer-term use.
Notice the apparent contradiction: Our 100 lb cover stock is 271 gsm, while our 110 lb index stock is 199 gsm. The lower pound number is the heavier sheet because cover and index use different basis sizes.
Side-by-side comparison
| Feature | Index stock | Cover stock |
|---|---|---|
| Paper category | Traditionally associated with cards, records, tabs, and filing | Broad card and printed-piece category associated with covers and presentation materials |
| Pound rating | Calculated using the index basis size | Calculated using the cover basis size |
| Common strengths | Practical stiffness, frequent handling, sorting, and everyday utility | Wide variety of surfaces, substantial feel, print presentation, and premium applications |
| Writing feel | Varies by the individual sheet and finish | Varies by the individual sheet and finish |
| Best comparison method | Compare category, GSM, caliper, finish, stiffness, and the needs of the finished product | |
Three measurements. Three different answers.
GSM means grams per square meter. Because the measured area is standardized, it is the clearest starting point for comparing the weight of papers from different categories.
Caliper measures physical thickness. Two papers with similar GSM can have different calipers because fiber, compression, coating, and manufacturing affect the sheet.
Stiffness, smoothness, tooth, opacity, and flexibility affect writing and handling. These qualities cannot be predicted perfectly from GSM or caliper alone.
Technical reference: Case Paper Thickness and Caliper Tables
Which should you choose?
For everyday flash cards and high-volume systems, an index stock may provide the right balance of structure, quantity, and storage. For a firmer card with an especially smooth surface, an ultra-smooth cover stock may be worth the additional weight and cost.
The most expensive or heaviest paper is not automatically the best choice. Select the lightest sheet that still delivers the durability, writing feel, and presentation your project requires.
Paper choices made clearer
Explore our cardstock guide for weight recommendations, then shop index cards by size, format, color, and intended use.
Cardstock Weight Guide Shop All Index CardsFrequently asked questions
No. Index and cover are different paper categories with different basis sizes. Both can be used to make cards, but their pound ratings cannot be compared directly.
Not necessarily. In our card stocks, 110 lb index is 199 gsm while 100 lb cover is 271 gsm. The cover sheet is heavier despite its lower pound number because index and cover use different basis-sheet sizes.
Each paper category uses its own basis size when the pound rating is calculated. For example, the Debra Dale Designs 100 lb ultra-smooth cover stock is 271 gsm, while its 110 lb index stock is 199 gsm.
No. GSM measures weight per square meter, while caliper measures physical thickness. Fiber, compression, coating, and finish can cause papers with similar GSM to have different thicknesses.
Both can make excellent flash cards. Index stock is a practical choice for everyday and high-volume card systems. Cover stock can provide a firmer or more refined surface when the specific sheet, finish, and weight suit the intended use.
Compare the paper category, GSM, caliper, finish, stiffness, writing performance, number of cards, storage method, and how often the finished cards will be handled.