Tesla’s Model 3 version with 75 kWh battery pack has been officially rated: The EPA confirmed the company’s own estimation, labelling the car with a city driving range of 321.9 miles (518 km), a highway range of 295.5 miles (476 km) and thus with a combined range of 310 miles (499 km).

Like more and more EV manufacturers, Tesla voluntarily asked to lower the EPA rating in order to avoid a striking discrepancy between the official figures and real-world usage. The EPA specifications are the official performance figures for EVs in the States.
insideevs.com, electrek.co