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FFT bins and window
Compare FFT frequency-bin spacing with the duration of the actual captured sample block.
Sample rate (Hz): 8000–384000; Captured samples (integer): 16–1048576; FFT size (power of two): 16–1048576
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FFT bins and window
Sample rate (Hz): 48000 Captured samples (integer): 4096 FFT size (power of two): 4096
- Frequency-bin spacing (Hz)
- 11.718750
- Captured block duration (ms)
- 85.333333
Bin spacing = sample rate / FFT size; captured block duration = 1000 × captured samples / sample rate. Enter sample rate 8,000–384,000 Hz, allowing fractions; captured samples and FFT size must be integers 16–1,048,576. FFT size must be a power of two and at least the captured sample count. Extra FFT points represent zero padding, not additional recorded samples. Padding makes frequency bins more closely spaced without lengthening the captured block or improving its ability to resolve nearby tones. Actual resolving bandwidth depends on captured duration and the analysis window; bin spacing alone is not resolution bandwidth. This is a settings calculation, not an FFT of uploaded audio, a latency estimate, a window correction or an amplitude measurement. It excludes overlap, averaging, leakage, calibration and processing time. Display uses six decimals without intermediate rounding.
Methodology
How it works
Bin spacing = sample rate / FFT size; captured block duration = 1000 × captured samples / sample rate. Enter sample rate 8,000–384,000 Hz, allowing fractions; captured samples and FFT size must be integers 16–1,048,576. FFT size must be a power of two and at least the captured sample count. Extra FFT points represent zero padding, not additional recorded samples. Padding makes frequency bins more closely spaced without lengthening the captured block or improving its ability to resolve nearby tones. Actual resolving bandwidth depends on captured duration and the analysis window; bin spacing alone is not resolution bandwidth. This is a settings calculation, not an FFT of uploaded audio, a latency estimate, a window correction or an amplitude measurement. It excludes overlap, averaging, leakage, calibration and processing time. Display uses six decimals without intermediate rounding.
Method and assumptions documented by Techrider.live
2026-11-01
Frequently asked questions
Does a larger FFT always resolve closer tones?
No. Adding zeros to the same captured block interpolates the spectral grid. To gain real information you need an appropriate longer capture and analysis window; closely spaced bins alone do not guarantee distinct tones.