What Determines How Many Photos Fit
Memory card capacity is fixed — a 128GB card holds 128 gigabytes of data. What varies is the file size of each photograph, which depends on three main factors:
- Megapixel count: Higher-resolution sensors produce larger files. A 45MP camera produces RAW files roughly twice the size of a 20MP camera's at similar compression settings.
- File format: RAW files preserve all sensor data and typically run 20–100MB each depending on resolution. JPEGs are compressed in-camera and typically run 5–20MB. The tradeoff is editing flexibility vs. file size.
- Scene complexity: JPEG compression is more effective on simple scenes (clear sky, flat surfaces) than complex ones (foliage, crowds, textured surfaces). RAW file sizes also vary slightly by scene but less dramatically than JPEG.
Photo Capacity by Card Size and Resolution
The table below shows approximate photo counts for common card sizes, camera resolutions, and file formats. RAW figures assume typical compressed RAW average file sizes. JPEG figures assume high-quality in-camera compression (fine/large setting).
| Card Size | 20MP RAW | 20MP JPEG | 24MP RAW | 24MP JPEG | 45MP RAW | 45MP JPEG |
|---|---|---|---|---|---|---|
| 32 GB | ~1,000 | ~3,200 | ~820 | ~2,700 | ~450 | ~1,600 |
| 64 GB | ~2,000 | ~6,400 | ~1,640 | ~5,400 | ~900 | ~3,200 |
| 128 GB | ~4,000 | ~12,800 | ~3,280 | ~10,800 | ~1,800 | ~6,400 |
| 256 GB | ~8,000 | ~25,600 | ~6,560 | ~21,600 | ~3,600 | ~12,800 |
| 512 GB | ~16,000 | ~51,200 | ~13,120 | ~43,200 | ~7,200 | ~25,600 |
RAW File Sizes by Megapixel Count
RAW files are not as compressible as JPEGs, but most modern cameras use lossless or lossy RAW compression. Typical average file sizes:
- 20MP cameras: 25–35MB per RAW file on average
- 24MP cameras: 28–40MB per RAW file on average
- 36MP cameras: 42–55MB per RAW file on average
- 45MP cameras: 55–80MB per RAW file on average
- 60MP+ cameras: 80–120MB per RAW file on average
Some camera manufacturers offer compressed RAW options (often labeled "cRAW," "sRAW," or "Compressed RAW") that produce smaller files — sometimes 30–50% smaller — with minimal impact on image quality. If your camera supports this, it effectively doubles your RAW capacity on any card.
JPEG File Sizes and Variables
JPEG file sizes vary more than RAW because the compression algorithm responds to scene content. At the same quality setting, a portrait against a blurred background will produce a smaller file than a wide landscape with fine foliage detail.
Typical JPEG file sizes at the highest in-camera quality setting:
- 20MP JPEG (Fine/Large): 7–12MB average
- 24MP JPEG (Fine/Large): 8–14MB average
- 45MP JPEG (Fine/Large): 14–22MB average
Reducing in-camera JPEG quality (from Fine to Normal or Basic) roughly halves file size again but produces visible quality loss at 100% zoom and in large prints.
How Many Cards to Bring
For professional or high-stakes shoots, the general rule is to bring enough capacity to shoot 3–5x what you expect to capture — and at least two cards. Redundancy matters because a card failure during a wedding, event, or commercial shoot has no remedy if you only had one card.
A practical approach for a full-day shoot with a 24MP camera shooting RAW:
- Wedding or long event (600–1,200 shots): Two 64GB or one 128GB card minimum
- Portrait session (150–400 shots): One 32GB card is sufficient with room to spare
- Sports or fast-burst work: Prioritize write speed as well as capacity
Card Speed vs Card Capacity
Card speed (measured in MB/s) and card capacity (measured in GB) are independent specifications. A fast card does not hold more photos than a slow card of the same size. Speed determines how quickly the buffer clears when shooting bursts and how fast files transfer to a computer.
For still photography at moderate frame rates, a UHS-I card is sufficient. For high-speed burst shooting (10fps+) or recording 4K video, a UHS-II or CFexpress card provides the write speed needed to prevent the buffer from filling and interrupting shooting. Buy the capacity you need first, then buy the speed rating the camera requires.
Frequently Asked Questions
Why does my camera show a different photo count than the table?
Camera manufacturers calculate available shots based on an average file size estimate, which varies by scene complexity, ISO, and compression. Simple scenes with flat colors produce smaller files than complex scenes with fine detail. The camera's estimate is an approximation — actual capacity depends on what you are shooting.
Should I use one large card or multiple smaller cards?
Professionals often prefer multiple smaller cards to reduce risk. If a single large card fails mid-shoot, you lose everything. Two smaller cards mean a failure costs half the shoot at most. The trade-off is managing multiple cards during a session.
How does shooting RAW+JPEG affect capacity?
When shooting RAW+JPEG simultaneously, each frame writes two files. Capacity drops to roughly half compared to shooting RAW only. Most photographers shoot RAW only and generate JPEGs in post rather than doubling storage requirements in-camera.
Does card speed affect how many photos fit?
No. Card speed (MB/s) determines how fast files are written, not how many can be stored. Capacity is determined only by card size. Speed matters for burst shooting and video recording, not storage count.
Are the photo counts in the table guaranteed?
These are reliable estimates based on typical average file sizes for each resolution and format. Actual counts vary by camera model, compression setting (some cameras offer multiple RAW compression levels), and scene complexity. Use them for planning purposes rather than as precise guarantees.