Ice Thickness Chart: How Thick Ice Needs to Be

An ice thickness chart lists the minimum clear ice that state agencies recommend before you walk, ride or drive onto a frozen lake. The Minnesota DNR starts at 4 inches for anyone on foot, and no thickness makes ice completely safe.

The ice thickness chart at a glance

The figures below come from the Minnesota DNR’s 2026 Danger! Thin Ice card, which titles them “Recommended Minimum Ice Thickness.” They are minimums for new, clear ice, not a promise that the ice under you will hold.

The same card prints one line in capital letters twice: ice is never 100% safe. Read the chart as the point where going out becomes reasonable to consider, then let what you measure on the lake make the final call.

How thick does ice need to be to walk on

Four inches is the number you will see most often. The Minnesota DNR puts “on foot” at 4 inches and tells you to keep off anything thinner. The National Weather Service says ice fishing, skating and walking need 4 inches or more, and North Dakota Game and Fish lists 4 inches of good ice for a walking individual.

That 4-inch figure assumes clear, newly formed ice. The DNR card is blunt about the gap between thickness and strength: 4 inches of clear new ice may support one person on foot, while a foot or more of old, partially thawed ice may not. So the honest answer to how thick ice needs to be to walk on is “4 inches of the right kind of ice, confirmed with your own test holes.” Once you have that, our ice fishing gear guide covers what else to bring onto the lake.

Why other charts show different numbers

Search for an ice thickness chart and you will find several versions that do not quite agree. Here is how three public agencies compare on the activities they each list.

The spread comes from rounding and from how each agency groups vehicles, not from one of them being wrong. When two charts disagree, plan around the higher number. Nobody ever went through the ice because they waited for an extra inch.

White ice, snow cover and old ice

Every figure above refers to clear ice. The National Weather Service states that white or “snow” ice is only about half as strong as new, clear ice, and says to double the thickness guidelines when you travel on white ice. Under that rule, a walk that needs 4 inches of clear ice needs about 8 inches of white ice.

Snow causes trouble in two other ways. The Minnesota DNR notes that a snow blanket insulates the ice and slows freezing, and that its extra weight reduces how much load the ice sheet can carry. North Dakota Game and Fish makes the same point about insulation preventing clear, blue ice from forming. Shovel the snow off before you judge thickness and color. The Wisconsin DNR adds that clear ice is generally stronger than ice with snow on it or bubbles in it, and both Minnesota and North Dakota say new ice is usually stronger than old ice.

Where the ice is thinner than the chart suggests

A chart gives you one number for a whole lake. Real ice does not cooperate. The Minnesota DNR says ice seldom freezes uniformly and can be a foot thick in one spot and only an inch or two a few feet away. Ice near shore can be weaker than ice farther out.

Moving water is the usual culprit. The DNR flags streams, springs, channels between lakes, bridges, culverts and aeration systems, and notes that ice on the outside bend of a river is usually weaker because the current runs faster there. Wisconsin’s list adds inlets, outlets and narrows. Watch for large cracks, depressions and pressure ridges, and give them a wide berth. The National Weather Service also tells you to stay off ice with flowing water around its edges or over the top, and ice that looks like it thawed and refroze.

How to check ice thickness yourself

The Minnesota DNR’s ice safety kit is short: rope, ice picks, an ice chisel or drill, and a tape measure. Check thickness at regular intervals as you walk out instead of trusting one hole at the access point. North Dakota Game and Fish also recommends drilling test holes to judge thickness. An ice chisel lets you check the ice ahead of you, and any auger, hand or powered, gives you a reading every time you open a hole; our ice auger comparison sets hand, gas and electric models side by side.

Before you leave home, check recent weather rather than the calendar, as the DNR puts it, and ask locally. Wisconsin’s DNR says outright that it does not monitor local ice and points anglers to bait shops, fishing clubs and resorts, which see the ice every day.

Safety gear to carry with you

Thickness is only half of ice safety. The Wisconsin DNR lists ice claws or picks, a phone in a waterproof bag, a life jacket and a length of rope, and asks you not to go out alone. The Minnesota DNR adds wearing a life jacket or buoyant gear whenever you are on the ice outside a vehicle, and telling someone where you are going and when you expect to be back. If this is your first season, our ice fishing for beginners guide walks through a first trip from test hole to first fish.

Driving on the ice

The vehicle rows of an ice thickness chart are where mistakes cost the most. The Minnesota DNR’s advice starts with “Don’t drive on the ice if you can avoid it.” If you must, it says to avoid traveling at night, especially during snowfall or fog, to roll a window down and unlock the doors, and to keep a life vest close but not wear it inside the vehicle, where the bulk could slow your escape. North Dakota Game and Fish also warns against driving at night or during snowfall.

If you do go through on foot, the Minnesota DNR’s self-rescue steps are worth memorizing before the season: control your breathing, keep your winter clothes on, turn back toward the direction you came from, dig in with your ice picks and kick your way out, then roll away from the hole and get warm right away. Your state agency’s current guidance comes first, and no ice thickness chart replaces a test hole drilled where you are about to stand.