Half-life of a First-order Reaction Calculator
🔋 Rates & Electrochemistry. Use the Half-life of a first-order reaction formula to find half-life, rate constant k: pick the value you want, type the others, and the answer updates as you go.
Half-life69.315 s
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 |
|---|---|
| Half-life | s |
| Rate constant k | 1/s |
Worked example
Find the half-life when Rate constant k = 0.01 1/s.
Using t1/2 = (ln 2)/k: Half-life = 69.315 s.
Frequently asked questions
What is the formula for Half-life of a first-order reaction?
t1/2 = (ln 2)/k.
What do the letters stand for, and what units are used?
Half-life in s, Rate constant k in 1/s.
How do you calculate half-life?
Put the values into t1/2 = (ln 2)/k. For example, with Rate constant k = 0.01 1/s, half-life = 69.315 s.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (half-life, rate constant k) and fill in the others: it rearranges the formula for you.
