The largest size a planet can be without being pulled into a sphere by its own gravity depends on various factors, including its composition, mass, and rotation. However, there is a limit to how large a non-spherical planet can be before it collapses under its own gravity and becomes a roughly spherical shape.
This limit is often referred to as the "hydrostatic equilibrium" or "spherical shape" criterion. It occurs when the gravitational force pulling inward is balanced by the internal forces resisting compression, such as the strength of the planet's materials. Once a planet exceeds this limit, its own gravity will cause it to collapse into a spherical shape.
The exact threshold for this criterion depends on the material properties of the planet. For rocky or terrestrial planets, which have solid surfaces, the limit is generally thought to be around 600 to 1,000 kilometers (370 to 620 miles) in diameter. Beyond this size, the planet's gravity would be strong enough to pull it into a spherical shape.
However, for planets composed primarily of gas, like gas giants such as Jupiter and Saturn, the threshold is larger due to the lack of a solid surface. Gas giants can reach much larger sizes while still maintaining a non-spherical shape. Jupiter, for example, has a diameter of about 143,000 kilometers (89,000 miles) and is significantly larger than the rocky planets in our Solar System.
It's important to note that these size limits are rough estimates, and the actual boundary can vary depending on factors such as the planet's composition, density, and internal structure.