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Worksheet: Rule of the Square

Topic: endgame | Level: 3 | Week 9

Use an imaginary square to decide quickly whether a king can catch a running pawn.

Why This Matters

  • Count how many moves the pawn needs to promote. That number helps make the sides of the square.
  • If the defending king can step inside the square, it can usually catch the pawn.
  • The rule is a shortcut, but you should still check the actual moves when kings are close.

Objectives

  • Draw or imagine the square of a pawn race.
  • Decide quickly whether the king is inside the square or outside it.
  • Check your square idea by playing the race out move by move.

Practice Tasks

  1. Explain what the square starts from and how wide it is.
  2. Why is the rule of the square useful even before you calculate every move?
  3. Play out the three races and write whether the king catches the pawn or the pawn escapes.

Board Walkthrough

Follow the lesson one board at a time. The teacher answer key includes the move list.

Board 1
Board 2
Board 3
Board 4
Board 5
Board 6
Board 7

Practice Positions

Solve each position on paper first. Answers live only in the separate teacher/parent key.

Practice 1

White to move. Play out the race and show that the king is inside the square.

Practice 2

White to move. Play the race and prove that the king is outside the square.

Practice 3

Rook pawns have a funny-shaped race too. Play it out and show the king still catches this one.

Mini-Game

Play this with a partner. Before each king move, point to the imaginary square of the pawn and say whether the king is inside it or outside it.

Answer Key

Rule of the Square

Teacher/parent key for Worksheet: Rule of the Square.

Worksheet Answers

  1. Prompt: Explain what the square starts from and how wide it is.

    The square starts on the pawn’s square and reaches to the promotion rank with the same width as height.

  2. Prompt: Why is the rule of the square useful even before you calculate every move?

    It gives a fast yes-or-no answer before you calculate every move in detail.

  3. Prompt: Play out the three races and write whether the king catches the pawn or the pawn escapes.

    Practice 1: king catches. Practice 2: pawn escapes. Practice 3: king catches.

Model Line

  1. Kd4
  2. c3
  3. Kxc3
  4. Kg7
  5. Kd4
  6. Kg6

Practice Position Solutions

Rule of the Square — Practice 1

White to move. Play out the race and show that the king is inside the square.

Solution: Kd4 c3 Kxc3

The king steps into the square in time and catches the pawn on c3.

Rule of the Square — Practice 2

White to move. Play the race and prove that the king is outside the square.

Solution: Kf2 c1=Q

White is too far away. The pawn reaches the last rank before the king can catch it.

Rule of the Square — Practice 3

Rook pawns have a funny-shaped race too. Play it out and show the king still catches this one.

Solution: Kc3 a4 Kb4 a3 Kxa3

Even against the rook pawn, White stays close enough to enter the square and capture it on a3.