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Activity (Becquerel) Calculator

Work out activity (becquerel) instantly with clear inputs, formula shown and shareable results.

About Activity (Becquerel) Calculator

Activity is the decay rate, A = lambda.N, so it depends on both how many atoms are present and how unstable they are. 1e18 atoms with a one-day half-life give 8.02e12 Bq, or 217 curies. Because activity is proportional to N, it decays with exactly the same half-life as the sample itself.

Formulas

Activity

A = lambda N = (ln2 / t(half)) x N

Unit relation

1 Ci = 3.7e10 Bq

Worked example

With the default values below, Activity (Becquerel) Calculator returns Activity of 8.02254 × 10¹². Change any input above and every figure here is recalculated in your browser.

Inputs used

Number of radioactive atomsminimum 0
1,000,000,000,000,000,000
Half-lifeminimum 0 s
86,400 s

Results

Activity
8.02254 × 10¹² Bq
Same Activity In Curies
2.1683 × 10²
Decay Constant
8.0225 × 10⁻⁶ 1/s
Activity After One Half-Life
4.0113 × 10¹² Bq

Step by step

  1. 1Values used
  2. 2Activity
  3. 3Unit relation
  4. 4Activity= 8,022,540,000,000.00000 Bq
  5. 5Same Activity In Curies= 216.8250
  6. 6Decay Constant= 0.0000 1/s
  7. 7Activity After One Half-Life= 4,011,270,000,000.0000 Bq

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is a short half-life more dangerous?

It gives higher activity for the same number of atoms, but it also decays away quickly. Hazard depends on activity, radiation type and biological behaviour together.

Why is the becquerel such a small unit?

Because it is one decay per second. A banana registers about 15 Bq, which is why kBq and MBq are used in practice.

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