Calculate Doubling in a Time Span

Calculator for the time for doubling and other duplications. Some things double regularly, this is called exponential growth. Here you can calculate if something doubles within a time span, how many times it multiplicates in another time span or how long it takes to reach a certain amount. Please enter a start amount and the time span for doubling. Below, enter either the end amount or the time for calculation.

Amount 1:
*2 in:

Amount 2:


With a start value (amount 1) of 5 and an hourly doubling, after one hour 10 is reached, after 2 hours 20, after 7 hours 640. One hour before (-1 h), the amount was 2.5, at -2 hours it was 1.25. The amount 1 was at - 2 h 19 min 18,9 s.

Bacteria reproduce by cell division. Some bacteria do this every 20 minutes, then one bacterium becomes two. After 3 hours, 20 minutes, its number has multiplied by more than a thousand (1024 times). After one day, its number would have almost multiplied by 5 sextillions. This is only mathematically, in reality, growth has limits, which this calculator doesn't consider.

According to Moore's law, the number of transistors on an integrated circuit doubles approximately every 2 years (730.5 days) at the same cost. This law makes good predictions since the beginning of the 1990s, but it won't last forever.

The formula is:
z2 = z1 * log2(a2/a1)
a2 = a1 * 2z2/z1
a1 = amount 1, a2 = amount 2, z1 = time 1 in seconds, z2 = time 2 in seconds


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