Audio file size

Estimate audio size from its duration and total encoded bitrate. The formula is bytes = minutes × 60 × bitrate in kbit/s × 1000 ÷ 8 × (1 + reserve/100). Zero duration gives zero bytes. Bitrates may be fractional. A blank reserve is zero.

For constant bitrate (CBR), this estimates the encoded audio data. The optional percentage adds a reserve to that estimate; it does not inspect a container, metadata or padding. Variable bitrate (VBR) requires a representative average bitrate and remains an estimate. Use the total bitrate of all encoded channels: do not multiply an already combined stereo bitrate by two. Uncompressed PCM requires its corresponding total data rate.

SI units use powers of 1000: 1 kB = 1000 B and 1 MB = 1,000,000 B. IEC binary units use powers of 1024: 1 KiB = 1024 B and 1 MiB = 1,048,576 B. A byte contains eight bits. See NIST: prefixes for binary multiples.

The estimate may contain fractional bytes even though an actual file has an integer byte count. The byte display rounds to the nearest whole byte; kB and KiB show at most three decimal places, MB and MiB at most four. Each unit is converted from the unrounded estimate. Display rounding does not add padding or a guaranteed storage reserve.

This browser-number estimate is deliberately limited to 9,007,199,254,740,991 bytes, the largest safe integer in JavaScript. Larger or nonfinite results are rejected instead of displaying an apparently valid size. This is a calculation limit, not a file-format or filesystem limit.