I wrote this reply on redit to someone that said something to the effect that the Model S was closer in size to the ipace than the Model X. I thought I'd toss it here as well.
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The S and X are close to the same length and width (based on the same skateboard / battery pack / drivetrain)
https://motorchase.com/wp-content/uploads/2016/03/Tesla-skateboard.jpg
If you are looking for the smaller Teslas, you would be more right to say it's comparable to the Model 3 and Y .
* Model X Dimensions: 198.3" L x 89.4" W x 66.3 H
* Mode S Dimensions: 196" L x 86.2 W x 56.5 H
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* ipace Dimensions: 184″ L x 75″ W x 61″ H
* Model 3 Dimensions 184.8" L x 76.1 W x 56.8 H
Model 3 is closer in size by Length and width to the iPace.
iPace height is taller than 3 and S but shorter than X.