How is buffer depth calculated?

While you shoot, data arrives at burst rate × file size while the card simultaneously drains the buffer at its write speed, so the buffer fills at the NET rate. Frames before the buffer fills ≈ buffer ÷ (file size − write speed ÷ burst rate). For a 2GB (≈1900MB effective) buffer, 50MB RAW files at 10fps and a 90MB/s card writing at ~81MB/s, that is 1900 ÷ (50 − 8.1) ≈ 45 frames — noticeably more than the simple buffer ÷ file size figure of 38, because the card is draining the buffer as you shoot. The faster the card, the bigger the difference.

Why does card speed matter for buffer?

While shooting, the camera simultaneously writes from buffer to card. A faster card drains the buffer quicker, effectively increasing your burst depth and reducing recovery time between bursts. This is especially important for sports, wildlife and event photography.

How do I find my camera buffer size?

Camera manufacturers rarely publish exact buffer sizes. Check your camera manual for rated burst depths at various file formats. You can estimate the buffer by multiplying the rated RAW burst depth by your RAW file size. Typical buffer sizes range from 1GB to 4GB in modern cameras.

What is sustained shooting rate?

Once the buffer fills, shooting continues at the sustained rate — determined by how fast the card can write. Sustained RAW fps = card write speed ÷ RAW file size. A 90 MB/s card (≈81 MB/s after efficiency) with 50MB files sustains only about 1.6 fps, regardless of the camera burst rate. At its rated 90 MB/s it would sustain 1.8 fps, but real-world cards run a little below their rating.

Buffer Calculator — Buffer Depth & Write Speed

Estimate buffer depth from file size, write speed and burst rate for RAW and JPEG shooting.

RAW File Size

One RAW file (≈25-30MB for 24MP 14-bit, ≈45-60MB for 45MP)

JPEG File Size

One JPEG file at fine/large quality (typically 8-20MB)

Burst Rate

Camera's continuous shooting speed (frames per second)

Buffer Size

Camera buffer memory (estimate: rated RAW burst × RAW file size; 1000MB = 1GB)

Card TypeMemory card sustained write speed (faster cards drain the buffer quicker)

How We Calculate This

This calculator estimates buffer performance from file size, card write speed and burst rate. The key insight is that the card drains the buffer while you shoot, so the buffer fills at the net rate (data in minus data written out):

Buffer Depth (card draining)

Frames = effective buffer ÷ (file size − write speed ÷ burst rate)

If the card keeps up (write speed ≥ burst rate × file size) the buffer never fills and you can shoot continuously at the chosen frame rate.

Instantaneous Capacity

Frames = effective buffer ÷ file size — the static count if nothing drained; the real depth is always at least this large.

Burst Duration

Duration = buffer depth ÷ burst rate

Sustained Rate

Sustained fps = card write speed ÷ file size — the rate you can keep shooting once the buffer is full.

Effective buffer = buffer size × (1 − overhead%); effective write speed = card rating × write efficiency. Adjust both under Advanced options.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.