FFT Bin Resolution Planner
What frequency grid and time window does your FFT size create for a target tone?
Method, formula and assumptions
Bin spacing = sample rate / FFT size. Window duration = FFT size / sample rate. Choose the nearest frequency bin by rounding target frequency / bin spacing.
Input definitions and supported units
- Sample rate (Hz): Whole-number count, from 8000 to 384000; must be positive.
- FFT size (samples): Whole-number count, from 16 to 1048576; must be positive.
- Target frequency (Hz): Measured or assumed numerical value, from 0 to 192000; zero is supported where the stated method permits it.
Worked example with answer
48 kHz with 4,096 samples gives 11.7188 Hz spacing and an 85.3333 ms window. A 1,000 Hz target is nearest bin 85, whose center is 3.9063 Hz below the tone.
How to use the results
A longer window makes the bin grid denser while spanning more time. Bin spacing is not the same as the ability to resolve two tones after a window function.
Results retain full precision internally and display up to four decimal places. Very small nonzero results use scientific notation rather than appearing as zero. Check the labels before comparing values across units.
Limitations and references
Assumes a radix-two FFT and no zero-padding. Leakage, window shape, noise and interpolation influence real spectral measurements; inputs above Nyquist are rejected.
The method is a self-contained arithmetic, geometric or explicitly stated mathematical model. There are no imported tariffs, empirical presets or equipment specifications; measured values and allowances must come from your own process.
Related planning tools
Creator & reviewers
Creator persona
- Casey RowanUnits, conversions & measurement
Reviewer personas
- Devon ShawFormula & assumptions review
- Sage MitchellClarity & usability review