Half-life Calculator (t½ from k)

Half-life Calculator (t½ from Rate Constant)

Calculate half-life (t½) from the rate constant (k) for common reaction orders.

Inputs Reaction settings

Reaction order

0th order t½ depends on [A]₀ and k 1st order (default) t½ = ln(2) / k 2nd order t½ depends on [A]₀ and k

Rate constant (k)

Enter k as a positive number. Time basis defines the “per time” part of k.

Display t½ in

Default matches k’s time basis for a smoother workflow.

Initial concentration ([A]₀)

Required for 0th and 2nd order.

Custom unit label

Required when “custom” is selected (max 16 characters).

Unit expectations

For 1st order: k should be in 1/time.

This is guidance only; the calculator checks numeric validity.

Options Steps

Show Steps

ln(2) = 0.6931471805599453

Half-life

t½

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Output unit

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Equation used

Order

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Equation

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Time conversions

k basis

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Output

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Inputs

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[A]₀

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