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The 2, 4 and 8 Times Tables: Just Keep Doubling

Level 1 Times tables · Reviewed by The NumThink editorial team · Last reviewed

Short version: ×2 is doubling, ×4 is doubling twice, ×8 is doubling three times. 7 × 8: 7 → 14 → 28 → 56.

This page is part of the NumThink Times tables course. Read why the method works, watch it run on worked examples, then drill it in the practice box below until it feels automatic.

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Why it works

4 = 2 × 2 and 8 = 2 × 2 × 2, so multiplying by 4 or by 8 is the same as doubling two or three times. Doubling is the easiest mental operation there is.

It also links the tables: every ×8 answer is double the ×4 answer, and every ×4 answer is double the ×2 answer. Learn one, and the other two follow.

The steps

  1. Double once for ×2. 6 × 2 = 12.
  2. Double again for ×4. 12 → 24, so 6 × 4 = 24.
  3. Double a third time for ×8. 24 → 48, so 6 × 8 = 48.

Worked examples

Easy 9 × 2

Show the thinking

Double 9: 9 + 9 = 18

So 9 × 2 = 18.

Answer: 18

Medium 7 × 4

Show the thinking

Double 7 → 14

Double 14 → 28

So 7 × 4 = 28.

Answer: 28

Hard 12 × 8

Show the thinking

Double 12 → 24

Double 24 → 48

Double 48 → 96

So 12 × 8 = 96.

Answer: 96

When to use it

  • Every fact in the 2, 4 and 8 tables — including the famous hard ones like 7 × 8 and 8 × 8.
  • Beyond the table: 15 × 8 is 15 → 30 → 60 → 120, and 23 × 4 is 23 → 46 → 92.

When NOT to use it

  • 8 × 9 is quicker with the 9s rule: 8 × 10 − 8 = 72.
  • Facts you already know by heart — recall beats three doublings.

Common mistakes

Doubling the wrong number of times. Doubling only twice for ×8 (7 → 14 → 28). Fix: Count the doublings: ×2 once, ×4 twice, ×8 three times — 7 → 14 → 28 → 56.
Losing a carry while doubling. Doubling 48 and writing 86. Fix: Double the tens and the ones separately: 40 → 80, 8 → 16, and 80 + 16 = 96.
Check yourself: Every answer in these tables is even, and halving a ×8 answer gives the ×4 answer: 96 ÷ 2 = 48 = 12 × 4 ✓.