FIR Filter Designer

Design a digital low-pass filter from scratch. Add taps to sharpen the cutoff and watch the frequency response tighten in real time.

FIR Filter DesignerLive

windowed-sinc low-pass

Controls

Presets

Number of taps

Cutoff (× Nyquist)

An FIR filter convolves the signal with a set of tap coefficients. A windowed sinc gives a low-pass response whose transition band sharpens as you add taps — more taps mean a crisper cutoff but more computation and delay. Educational tool.

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Data Inspector

Taps21

Cutoff0.40 × Nyquist

Group delay10 samples

Governing equation

y [n] = k = 0 \sum 20 b_{k} x [n - k], f_{c} = 0.40 f_{Nyq}

Reading this result: 21 taps balance sharpness against cost — transition band ~0.31 × Nyquist, group delay 10 samples.

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How it works

A finite-impulse-response filter convolves a signal with a set of coefficients. Truncating an ideal sinc and applying a window yields a practical low-pass filter; more taps give a narrower transition band at the cost of computation and delay. Educational tool.

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The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.

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Frequently asked questions

Is this fir filter designer tool really free?▾

Yes. FIR Filter Designer runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.

Do I need to install anything?▾

No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.

Can I save or share my simulation?▾

Create a free account to save projects, and use a shareable embed or minted DOI to publish a live, interactive version anywhere.

How accurate are the results?▾

The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.