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Decay Constant Calculator

☢ Nuclear & Decay. Use the Decay constant formula to find decay constant λ, half-life: pick the value you want, type the others, and the answer updates as you go.

λ=ln⁡2T1/2\lambda = \dfrac{\ln 2}{T_{1/2}}
Decay constant λ0.13863 1/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

QuantityUnit
Decay constant λ1/s
Half-lifes

Worked example

Find the decay constant λ when Half-life = 5 s.

Using λ = ln 2T1/2: Decay constant λ = 0.13863 1/s.

Frequently asked questions

What is the formula for Decay constant?

λ = ln 2T1/2.

What do the letters stand for, and what units are used?

Decay constant λ in 1/s, Half-life in s.

How do you calculate decay constant λ?

Put the values into λ = ln 2T1/2. For example, with Half-life = 5 s, decay constant λ = 0.13863 1/s.

Can I solve for a different value?

Yes. In the calculator above, pick the circle next to any value (decay constant λ, half-life) and fill in the others: it rearranges the formula for you.

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