Ice Hockey Rules Explained: Offside, Icing and Penalties

The shape of the game

Players on ice	6 per team — 1 goalkeeper, 5 skaters
Game length	3 periods × 20 minutes of playing time
Minor penalty	2 minutes
Major penalty	5 minutes
Governing code here	IIHF (Olympics, World Championships)

Two features make hockey read differently from other team sports. The clock stops at every whistle, so 60 minutes of hockey takes over two hours. And players change on the fly, swapping in and out while play continues, so the six skaters on the ice are almost never the same six a minute later.

Everything else is variations on two stoppages: offside and icing.

Offside: the skates decide, not the stick

Attackers must not enter the attacking zone before the puck does. The IIHF states it directly: “Players of the attacking Team must not precede the puck into the Attacking Zone.”

The measurement is unusually precise, and it is worth knowing exactly:

• A player is offside when both skates are completely over the leading edge of the blue line before the puck crosses it.
• A player is onside if either skate is touching the line, or on their own side of it, at the moment the puck fully crosses.
• The skates are the determining factor, not the stick. A stick can be deep in the zone with no consequence.

The rulebook adds a nice piece of geometry: your own side of the line is defined by a plane rising vertically from the leading edge of the blue line. If your skate has not yet broken that plane when the puck crosses, you are onside — even if the skate is in the air above the zone.

And a detail that surprises people: you cannot be offside against your own puck. A player who crosses the line ahead of the puck is fine provided they have possession and control before their skates cross.

One more: if a team legally plays the puck back into their own defending zone while an opponent is already in there, the offside is simply ignored and play continues.

Icing: why teams can’t just dump it

Icing exists to stop a pressured team clearing the puck the entire length of the rink to buy a rest.

Under Rule 81, the centre red line divides the ice into halves. If a player shoots, bats or deflects the puck from their own half beyond the opposing goal line, play is stopped and the faceoff comes back to the offending team’s end — the opposite of what they wanted.

The clause most people miss is who it applies to. Icing is only called against a team of equal or superior numerical strength. A team that is short-handed while killing a penalty is allowed to ice the puck freely. That single exception is what makes penalty-killing survivable, and it is why a team down a player will happily fire the puck down the ice again and again.

Judging it is a two-part decision by the linesperson: first, will the puck cross the goal line; then, which player would touch it first. The call is made by the time the first player reaches the end-zone faceoff dots — and it turns on who would touch the puck first, not who reaches the dots first.

Penalties and the power play

A penalised player leaves the ice and sits in the penalty box. Their team plays short-handed, and critically, no substitute is allowed — that is the actual punishment. The other team is on a power play, usually five skaters against four.

• Minor penalty — 2 minutes. The standard sanction for most fouls.
• Major penalty — 5 minutes. For more serious offences.

Hockey is unusual in punishing teams by arithmetic rather than by awarding a free shot. Soccer gives you a free kick; rugby gives you a penalty kick; hockey takes a player away from the other side for a fixed number of minutes and lets you attack five-on-four.

Goals that don’t count

One rule catches out newcomers. If an attacking player puts the puck in the net by contacting it above the height of the crossbar — directly or via a deflection — the goal is disallowed. What matters is where the puck met the stick, not where the puck ended up.

The mirror case is deliberately kind to attackers: if a defending player strikes the puck into their own goal with a stick above crossbar height, that goal stands.

Three sports, one word, three meanings

Offside is the clearest example of unrelated sports inventing the same word for genuinely different ideas — and comparing them shows what each rule protects.

Sport	Offside is measured against	What it prevents
Ice hockey	A fixed line on the ice (the blue line)	Attackers camping in the zone before the puck
Soccer	The second-last opponent	Attackers goal-hanging behind the defence
Rugby union	The ball itself	Anyone playing from in front of their own ball

Hockey’s is the only one anchored to painted geometry, which is why it can be judged frame by frame against a physical line. Soccer’s offside moves constantly, because the line is wherever the defenders happen to be. Rugby’s needs no line at all — the ball defines it, which follows from rugby’s ban on the forward pass.

Same word, three unrelated solutions to three different problems. More explainers of this kind are in rules and techniques.

A note on the NHL

This page follows the IIHF rulebook, which governs the Olympics and World Championships. The NHL maintains its own separate rulebook, and while the fundamentals above are shared, details differ — rink dimensions, some penalty specifics, and elements of the icing procedure among them.

If you are watching the NHL and something does not match, that is usually why, and it is worth checking the NHL’s own rules rather than assuming one code is a summary of the other.

Basketball has the same split: FIBA governs the Olympics and the World Cup, the NBA writes its own rulebook, and the two differ on things as basic as how long a game lasts.