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Fast Fourier Transform (FFT) Calculator

Radix-2 Cooley–Tukey FFT of real or complex samples (3+4i, −2i): magnitude, phase, frequency bins and a bar plot, with Hann, Hamming and Blackman windows corrected for coherent gain and one-sided bins correctly doubled except DC and Nyquist.

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Fast Fourier Transform (FFT) Calculator works straight from this page — free, instant, nothing to install. It covers 3+4i, −2i — adjust any of them and the result follows immediately.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Fast Fourier Transform (FFT) Calculator do?

Radix-2 Cooley–Tukey FFT of real or complex samples (3+4i, −2i): magnitude, phase, frequency bins and a bar plot, with Hann, Hamming and Blackman windows corrected for coherent gain and one-sided bins correctly doubled except DC and Nyquist.

What does it take into account?

It factors in 3+4i, −2i. Change any of them and the output follows immediately.

When would I actually use this?

Checking a derivative or an integral you worked out by hand, finding where a function turns, and getting a numeric answer when no closed form exists.

What is the most common mistake?

Integrating across a discontinuity as if it were not there. A numeric method will happily return a finite value for an integral that diverges — check the domain before trusting the number.

How is Fast Fourier Transform (FFT) Calculator different from Fourier Series Coefficients Calculator?

They sit next to each other but answer different questions: Fourier Series Coefficients Calculator is the one to open when you need it to a₀, aₙ and bₙ over any period, computed exactly by integration by parts when f is a polynomial and by Gauss–Legendre quadrature otherwise, with the truncated series plotted against f so the Gibbs overshoot is visible. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Inverse Laplace Transform Calculator is the closest one after this: f(t) from a rational F(s) by partial fractions, handling repeated roots and irreducible quadratics — 3/((s+2)²+9) comes back as a damped sine — with every residue listed and the expansion checked against F(s) numerically.

What else is worth having open alongside it?

Laplace Transform Calculator and Z-Transform Calculator (with ROC) — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Symbolic results are exact; numeric ones come from adaptive quadrature or a standard step method, and the tool reports which. Where both are available, compare them — a large gap means the problem is ill-conditioned.

Further reading

All guides →
ExplainerThe Flat Pattern of a Cone Is a Sector, Not a CircleRoll a 50 mm cone 80 mm tall and its pattern is a 190.8° slice of a 94 mm circle. Flatten a nearly cylindrical lampshade and the pattern radius runs to 839 mm — the shallower the taper, the further away the apex.ExplainerA 1 % Drop Rate Does Not Mean One Hundred RunsAt 1 %, a hundred attempts give you 63.4 % — not certainty. Ninety per cent takes 230 attempts and ninety-nine takes 459, and more than a third of players are still empty-handed at a hundred.ExplainerFibonacci and the Golden RatioThe Fibonacci sequence adds each pair of terms to make the next; the ratio of neighboring terms homes in on the golden ratio φ ≈ 1.618. See how, and where the pattern turns up.ExplainerWhat Is a Z-Score? Standard Deviations Above the MeanA z-score is z = (x − μ) / σ — how many standard deviations a value sits from the mean. Learn how to compute it, read the standard normal curve, and turn it into a percentile.How-toHow to Find the Distance Between Two PointsUse the distance formula d = √((x₂−x₁)² + (y₂−y₁)²) to measure the straight-line distance between two points on a plane, with a worked example and the midpoint too.How-toHow to Calculate the Slope of a Line: Rise Over RunFind the slope of a line from two points with m = (y₂ − y₁) / (x₂ − x₁), and read what a positive, negative, zero, or undefined slope tells you.
Fast Fourier Transform (FFT) Calculator — OneKitly