FFT Bin Resolution Calculator
Bin width, capture time and which bin any frequency lands in — with the leakage warning when you're off bin-centre.
A tone OFF bin-centre smears into neighbours (spectral leakage) — that's the offset warning. Fix with a window (Hann trades a 1.5-bin-wide main lobe for −31 dB sidelobes) or choose fs/N so your tone lands on a bin (coherent sampling). Finer resolution costs TIME linearly — 0.1 Hz bins at 48 kHz demand a 10-second capture regardless of CPU power.
FFT Bin Resolution Calculator computes bin width, capture time and the bin index of any frequency — free, instant and private in your browser. Vibration analysts, audio engineers and SDR users sizing their FFTs use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About FFT Bin Resolution Calculator
FFT Bin Resolution Calculator computes bin width, capture time and the bin index of any frequency using the standard engineering relation: Δf = fs/N; capture T = N/fs; bin = round(f/Δf). Worked live: 4096 points at 48 kHz give 11.7 Hz bins from an 85 ms capture. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use FFT Bin Resolution Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use FFT Bin Resolution Calculator?
- ✓Implements the real formula — Δf = fs/N — with the substitution shown, not a black box
- ✓Built for vibration analysts, audio engineers and SDR users sizing their FFTs
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate fft bin resolution?+
Bin width, capture time and the bin index of any frequency follows Δf = fs/N; capture T = N/fs; bin = round(f/Δf). For example, 4096 points at 48 kHz give 11.7 Hz bins from an 85 ms capture. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why does my pure tone smear across several FFT bins?+
Spectral leakage — the tone doesn't complete an integer number of cycles in the window, so energy spills into neighbours. Apply a window (Hann is the workhorse: −31 dB sidelobes for a 1.5-bin-wide peak) or choose fs/N so the tone lands exactly on a bin.
Can more FFT points improve resolution without more data?+
No — zero-padding interpolates the display but adds no information. Resolution is bought with OBSERVATION TIME (T = N/fs): 0.1 Hz bins demand a 10-second capture whatever the processor. Averaging multiple FFTs reduces variance, not bin width.
Is the FFT Bin Resolution Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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