Work out doubles and halves instantly with clear inputs, formula shown and shareable results.
Doubling multiplies by two and halving divides by two; repeating either k times multiplies or divides by 2 to the power k. Doubling and halving is the fastest mental route to the 4, 8 and 16 times tables, and repeated doubling is a first taste of exponential growth.
Double and half
double = number x 2; half = number / 2
Repeated doubling
after k doublings = number x 2^k; after k halvings = number / 2^k
double = number x 2; half = number / 2. Doubling multiplies by two and halving divides by two; repeating either k times multiplies or divides by 2 to the power k.
Doubling and halving is the fastest mental route to the 4, 8 and 16 times tables, and repeated doubling is a first taste of exponential growth.
Enter number, double this many times. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.