Index Card Sizes: 3x5, 4x6, 5x8 and How to Choose
Updated: Nov 3
Paper index cards are widely loved and used across the world and come in a variety of sizes. The most common size in the USA is 3" x 5" (3x5). The second most popular is 4" x 6" (4x6). Other sizes include 5x8 and of course both larger and smaller specialty cards. These sizes are also the most popular in the UK and rest of the world. What sizes are index cards and which size is best for you depends mainly on how you intend to use them as we discuss in this article.
Quick answer: the standard index card sizes are 3 x 5 inches (by far the most common), 4 x 6 inches and 5 x 8 inches. In the USA, 3 x 5 is the everyday default. Smaller cards such as half size or quarter size are not sold as standard sizes - you cut them yourself from a sheet of card stock.
Index Card Sizes | Size In Inches | Size in Centimeters | Size in Millimeters |
|---|---|---|---|
3 x 5 | 3 x 5 in | 7.62 x 12.7 cm | 76.2 x 127 mm |
4 x 6 | 4 x 6 in | 10.16 x 15.24 cm | 101.6 x 152.4 mm |
5 x 8 | 5 x 8 in | 12.7 x 20.32 cm | 127 x 203.2 mm |
6 x 9 | 6 x 9 in | 15.24 x 22.86 cm | 152.4 x 228.6 mm |
In today's increasingly online environment the index card remains an important part of the working toolset. Do not be fooled by their small sizes - the index card is a powerful tool for both business and study to take handwritten notes, organize information and share with colleagues. In this article we review for you all the different index card sizes available (at the time of writing in 2026), the best use-case for each size, and the pros and cons of different sizes.
What are the Different Sizes of Index Cards?
Here is a definitive list of different card sizes. Please tell us if we have missed one!
3 x 5 inches
4 x 6 inches (see A6)
5 x 8 inches
2 x 3 inches (see A8)
2.2 x 2.5 inches
2 x 3.5 inches
5 x 7 inches
6 x 9 inches
A6 size (107mm x 153mm) or (4.1 x 5.8 inches)
A7 size (74 mm x 105 mm) or (2.9 x 4.1 inches)
A8 size(52mm x 74mm) or (2.0 x 2.9 inches)
While there are distinct card sizes, you can see some similar items like the close relationship between 4 x 6 and the A6 size for instance.
Summary of Use Cases for Index Cards
Size | Popular Use Cases |
|---|---|
3 x 5 | Flashcards, Study Aids, Quick Notes, Storyboards, Research |
4 x 6 | Flashcards, Recipes, Speaking Notes |
5 x 8 | Note Taking, Presentations, Drawing |
1/2, 1/4 and 1/8 Index Cards: What the Sizes Actually Mean
You will see 1/2, 1/4 and 1/8 index cards described in two completely different ways, and they are not the same thing. The first is a naming convention: the fractions are trade names for the standard sizes. The second is a cutting instruction: you take a standard card and cut it into pieces. Here is the size table for the naming convention, which is the one most people searching these terms are after.
Fraction name | Size in inches | Size in centimetres | Size in millimetres |
1/8 index card | 3 x 5 in | 7.62 x 12.7 cm | 76.2 x 127 mm |
1/4 index card | 4 x 6 in | 10.16 x 15.24 cm | 101.6 x 152.4 mm |
1/2 index card | 5 x 8 in | 12.7 x 20.32 cm | 127 x 203.2 mm |
So if you were searching for the size of a 1/4 index card, the answer is 4 x 6 inches. If you were looking for a 1/2 index card, you want a 5 x 8 inch card. And a 1/8 index card is the everyday 3 x 5. These are labels rather than measurements - a 1/2 card is not half of a standard sheet, and a 1/4 card is not half the area of a 1/2 card. Read the size off the table rather than working it out from the fraction.
You may also see these fractions used to mean what you get by cutting a card down. Using that method, each cut halves the longer side of the piece in hand, so a 3 x 5 card becomes a 2.5 x 3 inch half, then a 1.5 x 2.5 inch quarter, then a 1.25 x 1.5 inch eighth.
If you cut a 3 x 5 card | Size in inches | Size in centimetres |
Half card | 2.5 x 3 in | 6.35 x 7.62 cm |
Quarter card | 1.5 x 2.5 in | 3.81 x 6.35 cm |
Eighth card | 1.25 x 1.5 in | 3.18 x 3.81 cm |
Two quick answers to the questions that come up most often. A 3 x 5 index card is a 1/8 card under the naming convention, not a quarter. And a 5 x 8 index card is the 1/2 card. If a shop or supplier has quoted you a fraction without an inch measurement, ask which convention they mean - it is the fastest way to avoid an order that arrives at the wrong size.
Cutting Your Own Smaller Cards
If you want a card smaller than the smallest standard size, cutting is the normal way to get there. The manufacturers make the three standard sizes and leave the rest to you. You buy a sheet of index card stock, take it apart, and end up with cards that are exactly the size your project needs. A half card fits a pocket or a ring binder that a full card will not. A quarter card is the right size for a revision card, a category tab, or one line of a larger system.
Half cards - half of a standard card. Useful for quick reference notes, or as dividers inside a card box.
Quarter cards - small enough to file in a ring binder or stick on the edge of a page, but still large enough to write on.
Eighth cards - slips rather than cards. Mostly used for labelling, tabbing and colour coding within a larger stack.
Cut them from card stock rather than plain paper so they still take ink, and so they do not curl in a ring binder.
Perforated card stock such as Avery 5388 is the easiest to cut, since the perforations show you where the cards separate.
Cut one sheet into a couple of sizes at once if you are unsure which size you will settle on, and keep the offcuts.
A practical tip: write on the uncut sheet first, then cut. You will waste far less card stock working out your layout at full size and cutting at the end, and you can re-cut a single card later if your system changes.
3 x 5 Index Cards
3 x 5 index cards (also referred as '3x5' or 3" by 5") are three inches tall by five inches wide (76.2 by 127.0 mm) and are by far the most common size - whether as ruled index cards (index card lined) or blank cards.
They typically look like this - this is an example of a pack of Oxford brand ruled index cards.
A 3 x 5 size ruled index card is great for taking notes, using for flash cards and storing small amounts of information like small to do lists or shopping lists. They are by far the most popular - in our research we found that the 3x5 index card is the most popular form available in store both lined or as blank index cards. We were recently at a CVS Pharmacy in West Los Angeles and you can see an example of a stack they had in stock.
4 x 6 Index Cards
4 x 6 index cards (also referred as ' 4x6' or 4" by 4") are four inches tall by six inches wide (101.6mm by 154.4 mm)
They typically look like this:
Usually available ruled, index cards in white measure 4x6 inches and the slightly larger size helps to organize larger lists and notes, to record presentation notes, store project research, manage projects, and store recipes for instance.
These are by and large interchangeable with people using a 3 x 5 size. They also seem to be more popular and the standard size in the UK.
An Amazon search between amazon.com and amazon.co.uk shows that the #1 index card size shown in the USA is 3 x 5 inches size, yet the same search query on amazon.co.uk brings up 4 x 6 inches size first also similar but not exactly the same as A6 size (4.1 x 5.8 inches). Interesting right? It shows that across the world different sizes become more standard for a variety of reasons and cultural history.
Is an Index Card 4x6?
Not Always. While the Oxford rulers' white index card measures four inches by six inches (4 x 6), that is not the only standard size. The typical standard index card size in the United States is three inches by five inches (3 x 5). They can come in a variety of sizes - if you visit your local stationery store in the office supplies / office products section you will see.
Is a 4x6 Index Card Bigger Than a 3x5?
Yes. A 4 x 6 card gives you 24 square inches of writing space, against 15 square inches on a 3 x 5 card - 60% more room on the same kind of card.
The extra space on a 4x6 is worth it when you are writing more than a short note:
Study notes where a single side needs more than a sentence or two.
Recipes and reference material, where the writing is dense.
Speaking notes and prompts for a presentation.
The trade-off is portability. A 4x6 is noticeably less convenient to carry and less likely to fit an index card box or a small card holder, so if you are writing quick notes and want them to go everywhere, 3x5 is still the better answer. The two are largely interchangeable in practice, and plenty of people buy both.
What Size are Large Index Cards?
Larger index cards are seen in the size range of 5"x 7", 5"X8" and 6" x 9".
These tend to be used for larger projects or display purposes.
What is the Largest Index Card?
In our research we found the largest 'index cards' to be 8.5" x 11" - but this is the US standard letter size. True 'largest' we would say is 6 x 9 inches like this:
Giant index cards could exist and be bigger but then I think we are in the realm of just large thick card paper!
What is the Thickness of an Index Card?
Index Card physical size is also determined by the thickness of the card. Thickness of an index cards ranges from 11pt to 25 pt (0.011" to 0.025"). The thickness of a card is often overlooked and can dramatically affect the perceived user experience and use case desired. Many people prefer the heavy weight card so it feels solid in the hand and more durable.
In our research we found the following average card thickness for the different sizes to be as follows:
Standard: 11pt thickness (0.011") Heavyweight Oxford brand. 0.011" is also referred to as 100lb stock. Heavyweight thickness index cards
Thin: You can get thinner ones, 7pt, 0.007" but user reviews indicate that these are too thin to be used as flashcards since the paper is too thin and your answer on the back of the card shows - be careful when selecting the right index card thickness and check the thickness. On the other hand, if you are using them as a pack in your back pocket to take quick notes then you might prefer a thinner card. Here is example of thin index cards
Thick: If you are looking for really thick cards look for thickness greater than about 100lb card stock (greater than 11pt). You can find some cards with 14pt (0.014") and higher. For example 17pt index cards
Some people even say that the heavyweight cards are not a good as they used to be in the old days, but this is what the tradeoff is in using paper cards today and trying to be economical and also saving the environment and trees. A better alternative is to use an app to create digital index cards using an app like NoteDex that creates life-like index cards on your computer and save paper!
Printing and Customizing Your Index Cards
Once you have chosen a size, the next question is how to get it onto paper. Most people print their own cards rather than buying them pre-cut, because it lets you set the layout, the ruling and the number of cards per sheet yourself.
Two things to decide:
First, whether you are printing onto card stock or onto ordinary paper you will cut down afterwards. Card stock is the better choice - it takes ink without bleeding and does not curl. Perforated index card stock, such as Avery 5388, is the easiest option, because the perforations show you where the cards separate.
Second, whether you want one card per sheet, or several cards printed together and cut apart. NoteDex prints 3 cards on one page, 4 in a 2x2 layout, or 9 in a 3x3 layout, so you can choose a sheet layout that matches the stock you bought.
We have a full walkthrough of the printing setup, including page size, margins and troubleshooting, in our guide to how to print on index cards - and if you would rather print on ready-made blank cards, there are Avery 5388 templates to download as well.
Tips for Choosing the Right Index Card Size
To pick the right paper index card size for you determine what you need to do with the index card and also how you want the card to feel in your hand (or your back pocket!)
If you are using index cards for small notes or data or as flashcards, then 3x5 size is good - but don't forget to check the thickness - especially if you are writing answers on the back of the card.
If you want to write more information - such as study notes, use for project management, recipes, or use as visual aids, you might prefer a larger size like 4x6 or 5x8 so they can be seen easily such as on a wall or spread out on a table.
Do you need a particular brand shop version? No, we don't think so as long as it meets your size and thickness criteria. You can find good index cards in nearly any store today, and of course in all the office products stores such as Office Depot, Walmart, or online at Amazon.
What about printing index cards? If the size fits your printer then it will also be important to check if the paper is too thin (or too thick) to pass through the printer. Some printers also will on only print one side, others two sides, but they will move the paper on its rollers usually so the thickness will also be a consideration.
Conclusion
Paper index cards still remain today an amazing tool to help capture ideas and share information. As you can see there are many considerations to pick the right size of index card for you.
If you like using index cards you might also consider using an online index card tool like NoteDex where you can create, share and print an unlimited amount of cards - and no trees will be used!
