General Ice Thickness Guidelines – For New, Clear Ice Only:

• 2″ or less: STAY OFF
• 4″: May allow ice fishing or other activities on foot
• 5″: Often allows for snowmobile or ATV travel
• 8″ – 12″: Supports most cars or small pickups
• 12″ – 15″: Will likely hold a medium sized truck.

Get more information on ice safety

Source: Maine Game Wardens