Half-life Calculator
⚛ Modern physics. Use the Half-life formula to find left after time t, starting amount, time, half-life: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Left after time t | no unit |
| Starting amount | no unit |
| Time | years |
| Half-life | years |
Worked example
Find the left after time t when Starting amount = 1000, Time = 15 years, Half-life = 5 years.
Using N = N0(1/2)^(t/T1/2): Left after time t = 125.
Frequently asked questions
What is the formula for Half-life?
N = N0(1/2)^(t/T1/2).
What do the letters stand for, and what units are used?
Left after time t, Starting amount, Time in years, Half-life in years.
How do you calculate left after time t?
Put the values into N = N0(1/2)^(t/T1/2). For example, with Starting amount = 1000, Time = 15 years, Half-life = 5 years, left after time t = 125.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (left after time t, starting amount, time, half-life) and fill in the others: it rearranges the formula for you.
