Solve the 4 and 8 times tables by doubling
Double a number twice to multiply it by 4. Double it three times to multiply it by 8.
Take 7 × 8. You do not need to recall it as a separate fact. Start with 7 and double it to 14. Double 14 to get 28, then double 28 to get 56. Three easy doubles give you 7 × 8 = 56. The same idea works for every number because 4 is 2 × 2 and 8 is 2 × 2 × 2.
Turn 7 into 7 × 8 with three doubles
Start with one 7. Every step doubles the amount, so the multiplier changes from 1 to 2, then 4, then 8.
×47 → 14 → 28 ×87 → 14 → 28 → 56
How to calculate 6 × 8 in your head
Keep doubling the last answer. Stop after the third double.
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Double 6
6 + 6 = 12
You now have 2 groups of 6.
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Double 12
12 + 12 = 24
You now have 4 groups of 6, so 6 × 4 = 24.
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Double 24
24 + 24 = 48
You now have 8 groups of 6, so 6 × 8 = 48.
Use the same doubling path with any number
For the 4 times table, stop after two doubles. For the 8 times table, double once more.
9 × 4
9 → 18 → 36
= 365 × 8
5 → 10 → 20 → 40
= 4012 × 8
12 → 24 → 48 → 96
= 96Why each double changes the multiplier
Doubling means making two copies of the amount you already have. That is why the number of equal groups also doubles.
One double means ×2
Start with 7. One double gives 14, which is 2 × 7.
Two doubles mean ×4
Double 14 to get 28. You doubled twice, so you now have 4 × 7.
Three doubles mean ×8
Double 28 to get 56. One more double turns 4 groups into 8 groups.
Now try 11 × 8
11 × 8 = ?
Start at 11 and double three times. What numbers do you pass on the way?
Show the answer Hide the answer
Double 11 to get 22, double 22 to get 44, then double 44 to get 88.
When repeated doubling is useful
Use the method whenever you need four or eight equal groups. It also helps you rebuild a times table fact you have forgotten.
Count four equal groups
Four boxes with 13 items each: double 13 to get 26, then double 26 to get 52.
Count eight equal groups
Eight rows with 7 seats each: 7 becomes 14, then 28, then 56 seats.
Try the method while you play
For every question, start with the other number. Double twice for ×4 or three times for ×8.
Questions about doubling for the 4 and 8 times tables
Why do I double twice for the 4 times table?
The first double multiplies the number by 2. The second double multiplies it by 2 again. Since 2 × 2 = 4, two doubles multiply the starting number by 4.
Does this work when 4 or 8 is written first?
Yes. Multiplication works in either order. For 8 × 7, start with 7 and double it three times, just as you would for 7 × 8.
What if a double feels difficult?
Split the number into tens and ones. To double 28, double 20 to get 40 and double 8 to get 16. Then add 40 + 16 = 56.
Should I still learn the times tables by heart?
Facts you use often may become automatic. Until then, doubling gives you a reliable way to find the answer instead of guessing.