Usually, two:
For front-wheel-drive cars and similar vehicles, it's generally sufficient to install snow chains on the front wheels. Since the front wheels are the drive wheels, responsible for forward propulsion and steering control, they are more prone to slipping on snow or icy surfaces. Installing snow chains effectively enhances the front wheel traction, improving the vehicle's starting, acceleration, and steering performance, thus ensuring driving safety.
In special cases, four:
If you frequently drive in areas with deep snow, thick ice, or extremely complex road conditions, you can choose to install snow chains on all four wheels for better stability and anti-skid performance. This further improves the vehicle's overall grip and handling, reducing the risk of skidding and loss of control.