If you are setting up a Raspberry Pi for the first time, the microSD card is the one part you should not buy on price alone. The card holds the operating system, so a slow or unreliable card makes the whole Pi feel slow, causes long boot times, and can corrupt files when power is lost. This guide is for first-time Pi owners and for anyone replacing a card that has started to show errors.
Verdict up front: buy a reputable-brand card in the 32 GB to 64 GB range, with A1 or A2 application performance class and U3 and V30 speed classes, from a seller you trust. If the Pi will run all day, every day, read the endurance guide instead and choose an endurance line. For a general-purpose Pi, the class and the seller matter more than chasing the largest capacity.
Win32 Disk Imager is a Windows-only tool, version 1.0.0 from 2017-03-08, and it writes a complete disk image to the card. That means the image must fit on the card, and the card should be tested before you trust it with a project. Our flashing walkthrough is covered in how to flash Raspberry Pi OS with Win32 Disk Imager, and the general workflow is explained in how to use Win32 Disk Imager.
What actually matters when you choose a card
Card marketing leans heavily on one headline sequential speed number. For a Pi, that number is not the whole story. The operating system constantly reads and writes many small files, so random performance and sustained write behaviour matter at least as much as a peak sequential figure printed on the packaging.
- Application performance class (A1 or A2): these classes describe minimum random read and write performance for running apps from the card. They are a useful filter, but they are spec classes, not a guarantee of how a particular card behaves in your Pi.
- Video and bus speed classes (V30 and U3): V30 and U3 indicate a minimum sustained sequential write level. They help with large writes, such as flashing an image or recording video, but they do not by themselves tell you how the card handles small operating-system writes.
- Capacity: a larger card does not make a Pi faster. It gives you more room for files, logs, and future updates. A 32 GB card is enough for a basic desktop install; 64 GB is a safer default if you will install extra software or keep backups on the Pi.
- Endurance line versus standard line: standard cards are designed for cameras and phones with intermittent writes. Endurance lines are built for continuous writing, such as dashcams and always-on recorders, and they are the better choice for a Pi that never sleeps. See our endurance comparison for that case.
- Fake-card risk: counterfeit cards report a larger capacity than they really have, then silently corrupt data once the real capacity is exceeded. Buy from a reputable retailer, keep the packaging, and test a new card before you rely on it.
Comparison: which class of card fits which Pi use
| Use case | Recommended class | Capacity guidance | Notes |
|---|---|---|---|
| General desktop Pi | A1 or A2, U3, V30 | 32 GB to 64 GB | Best balance of price and responsiveness for most users. |
| Media centre or retro gaming | A2, U3, V30 | 64 GB to 128 GB | More room for media and game libraries; check the current price before sizing up. |
| Always-on server or camera recorder | Endurance line | 32 GB to 128 GB | Choose an endurance line, not a standard line; see the endurance guide. |
| Testing and learning | A1, U3, V30 | 32 GB | A smaller, known-good card is fine when you reflash often. |
For a current product line to start from, see this microSD card for Raspberry Pi on Amazon (Sponsored) — check the current price and confirm the capacity, A-class, and U3 and V30 markings on the product page before you buy. See our affiliate disclosure for how sponsored links work on this site.
What to avoid
- Unbranded or suspiciously cheap cards: if the price is far below every reputable brand for the same capacity, assume the capacity or the speed rating is not real.
- Buying from marketplace sellers with no track record: counterfeit cards are common in third-party listings. Prefer the brand store or a well-known retailer.
- Skipping the test: before you flash anything important, test a new card. Our guide to testing a card with h2testw shows how to spot a fake before it eats your data.
- Using a worn-out old card for a new project: if a card has already shown read errors or failed writes, retire it. A Pi that will not boot after flashing is often a card problem, covered in Raspberry Pi will not boot after flashing.
Before you flash
Once you have a card you trust, flash it with the correct image and verify the result. Win32 Disk Imager can verify an image after writing, and you can find the download on our download page. After a successful flash, if the Pi boots but the filesystem looks small, the fix is usually to expand it, as explained in expanding the filesystem after flashing. Keep a backup image of a working card, because reflashing from a known-good image is far faster than rebuilding a Pi from scratch.
Frequently asked questions
What size microSD card should I buy for Raspberry Pi OS?
For most Raspberry Pi OS installs, a 32 GB card is a comfortable minimum and a 64 GB card gives room for updates, extra software, and a few projects. Larger cards are only needed if you plan to store a media library or many large files on the Pi itself.
Is an A2 card always faster than an A1 card on a Raspberry Pi?
Not necessarily. A2 is a higher application-performance class on paper, but real speed on a Pi depends on the card reader, the Pi model, and random read and write performance, not just the printed class. Check independent reviews and the product page for the class markings rather than assuming the label alone guarantees speed.
Can I reuse a card I flashed with Win32 Disk Imager?
Yes. Flashing overwrites the card, but you can reflash it with a different image later. Just double-check the destination drive letter before every Write, because Write overwrites the entire destination drive.