Fast Fourier Transform (FFT) is the easiest way to show the dominant frequencies in a signal. FFT is an efficient algorithm to compute the discrete Fourier Transform and in its inverse. There are many distinct FFT algorithms which involves a wide range of mathematics, which starts from simple complex-number arithmetic to group theory and number theory too. You also need Microsoft Excel with the Data Analysis package.If you don’t have this you can install this under Tools or Add-ins.

In this article you will see how to perform a FFT graph in Microsoft excel.

**Step 1:**

First and foremost open a blank spreadsheet and then follow the following titles to the first cells in column A, B, C, D and E of your spreadsheet: Time, Data, FFT Frequency, FFT Complex, and FFT Magnitude.

**Step 2:**

You need to add your data to the “Data” column. It will be helpful for you to make a note of the number of data points that is samples in your list and taking into consideration the sampling rate at which your data is taken. Do not forget o write and label these two numbers somewhere in your spreadsheet.

**Step 3:**

In the “Time” column, you need to determine the time at which each point was taken. The easiest way to do this is to divide the total time by the number of data points.

**Step 4:**

Next you need to perform a Fourier Analysis of your data which can be either Data/Data Analysis/ Fourier Analysis. You have make sure that the input range is your entire data column and the output range is you entire FFT Complete column. This column is known as FFT Complex column because the Fourier Analysis function outputs a complex number.

**Step 5:**

In the very first cell of the “FTT Magnitude” column, you need to type the following equation: =IMABS (E2)

Now you need to drag this equation down so that it fills every cell in this column. This will turn all the complex numbers in the “FTT Complex” column into a real number so that we can use the dominant frequencies.

**STEP 6:**

Now we need to calibrate the axis A of the graph to show the dominant frequencies. It may prove beneficial if we create a separate column showing zero through the number of data points minus one (N-1). It will also help to create a separate cell with the following function:

=(S/2)/ (N/2) over here S is a sampling rate and N is the number of samples.

In the “FTT Frequency” column you need to type the following function:

=F2*SG$4

Here F2 is the appropriate number from the number column, and $G$4 denotes the function dividing the sampling rate by the number of samples. Now drag this function down to half of your data of your data points.

**Step 7:**

Now create a graph of “FTT Magnitude” column (Y axis) versus the “FTT Frequency” column (X axis). If all you have done is right then you should get a graph with peaks where the dominant frequencies are.

What is the physical meaning of the FFT Magnitude (Y-axis). How does it relate to the frequency?

Hi,

I came across your notes, while I was searching for a recipe to do FFT analysis on a data set using excel.

as easy as they seem, I am having a bit difficulty to follow the instructions.

is G4 equal to (S/2)/(N/2) where S is the sampling frequency, and N is the number of points. Why is it (S/2)/(N/2)? why did not you write S/N? How is it any different?

also why fft frequency equal to F2*G$4? is this the definition of fft frequency?

Thank you very much,

Oscar

I agree with Oscar. You have errors in your instructions and there must be steps missing…

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Every time I try to perform a FFT graph in Microsoft excel, I get stuck at the fifth step where we need to type the equation. Performing a FFT graph is not easy but thanks to the DIY solution here, I can now perform it easily. TechGenie has helped me to resolve many technical issues like this before.

I always end up doing something wrong while performing a FFT graph in Microsoft excel. I usually get confused at the equation step but the steps here are easy to follow and next time I will be able to do it on my own. I have a request that you please continue to give such DIY’s as it is of great help to the technically challenged people like me. TechGenie is a big hope for me and I always look forward to the information given here

It is assumed that the labels are all in row 1.

With regard to columns:

A = Time

B = Data

C = FFT freq

D = FFT complex

E = FFT Magnitude

F = ?, probably some numerical index

The author made a typo. Where it says

“Step 5:

In the very first cell of the “FTT Magnitude” column, you need to type the following equation: =IMABS (E2)”

It should have read (D2). This is because you are interested in the amplitude of the FFT’d signal. The FFT gives two important bit: amplitude and phase, but it *gives* the info as a complex number (ie real and imaginary components). One must break it down into its useful parts. That is my imabs is for:getting the amplitude.

Even after you have the amplitude ‘FFT MAGNITUDE’ (call it the Y axis), you somehow need to get the right values for the X axis-to match. This is where you are determining the scaling for the x-axis.

How do we do this? Well, the Nyquist theorem says the maximum frequency you resolve is half your sampling frequency in the time domain. It is for this reason that the frequency should only extent to +/- your sampling frequency (in the time domain) divided by two. After all why should we favor positive frequencies over negative ones? They are both will fit right over the top of a time domain signal-ie. cosine (for example) Now that you have the boundaries of your x axis, you need to divide that x-axis into N samples so that your x axis is the same size as your y axis. That is all the fancy ratio stuff that step 6 was trying to do. So your x axis would look like: {(-Fs/2), (-Fs/2)+ delta,

-(Fs/2)+2delta,…0,…,(Fs/2)-2delta,(Fs/2)-delta,(Fs/2)}

In this case Fs is the sampling frequency in the time domain. We could solve delta by thinking about breaking -fs/2 to fs/2 into N of delta or we could think about ranging from 0 to fs/2 (~half as many) divided by N/2 to obtain delta.

but if you really want to learn a lot about fourier techniques, I like the book “FFTs in NMR, Optical, and Mass Spectroscopy” Francis and Verdun (if I recall).

I had gone through the write-up and tried following the steps very carefully. But every time I try, I do not get a FFT graph. Please can you suggest what may be wrong on my application? I have some urgent work to do using excel and am not able to proceed. Please help!

Microsoft Excel has never been easy for me. Never have I been able to perform the formulas and equations. But when searching for some solution on how to do a FFT in Microsoft Excel I ended up here on this page. I faced some issues in the beginning but after trying for 2-3 times I understood and performed the task. Would like to thank for the solution.

Working on Microsoft Excel has always been tough for me, creating FFT graph was beyond my skills. But the other day I was looking for steps for creating FFT Graph and luckily I came across this page. Though, I was unable to create a FFT graph in the first attempt. But after several attempts I could easily create FFT graph.