A website that I respect and enjoy reading published this graphic-

It is just so wrong.

The dimension regulations for 2026 as published 10 June 2025 are complex as they are based on a right-handed Cartesian system.

The wheelbase is specified on two planes, Xf and Xr for front and rear respectively, and must be less than or equal to 3400mm at Legality Ride Height. This is 200 mm less than the current regulations. The Xf, front wheel plane, can deviate for up to 150mm which will further shorten the wheelbase.

In the current regulations the longest a car can be is 5630mm. Though not specified in the new regulations for 2026, the longest a car can be is 5480mm. This is shorter by 150mm. In theory, the greater the surface area of a car the greater the aerodynamic efficiency.

The cockpit position is also not fixed. The technical regulations rephrased for clarity “The distance between XA (the X−Plane that lies on the forward limit of the Survival Cel = 0) and XC (the X−Plane at the rear of the Cockpit = 0) must be greater than or equal to 1830mm and less than or equal to 2030mm”.

A bit more clarity-

The above drawing is to illustrate the technical regulations as interpreted by me. It is not an engineering drawing by any means. The teams do not publish details of their construction dimensions as this is their intellectual property.

For a side view of the car the maximum dimensions for length and wheelbase will be-