Radioactivity volume concentration unit converter

This radioactivity volume concentration converter allows users to convert between commonly used activity concentration by volume units, including SI becquerel-based quantities and legacy curie-based quantities that continue to appear in monitoring reports, environmental sampling records, discharge documentation, international guidance, and training materials.

It is intended to support clear communication, sense-checking of values, and consistent interpretation of volume-based activity concentration across different regulatory, technical, and educational contexts.

What this calculator does

Radioactivity (activity) describes the rate of radioactive decay. When activity is expressed per unit volume, it becomes a volume activity concentration (for example, Bq/m³ or Bq/L), widely used for:

  • airborne activity concentrations (workplace air monitoring, environmental air monitoring);

  • liquids and effluents (water samples, discharges, process liquids);

  • reporting and comparison of sampling results across different measurement conventions.

In UK and international practice, volume activity concentration is commonly expressed using Bq/m³ (air) and Bq/L (liquids). However, older documentation and some non-UK sources may use pCi/L, pCi/mL, or related curie-based expressions.

This calculator provides straightforward conversion between volume activity concentration units using accepted, fixed relationships for both:

  • activity units (Bq and Ci families), and

  • volume units (millilitre, litre, cubic metre).

Supported volume concentration units

The calculator supports conversion between the following volume activity concentration units:

SI units (becquerel-based)

  • millibecquerels per millilitre (mBq/ml), becquerels per millilitre (Bq/ml), kilobecquerels per millilitre (kBq/ml), megabecquerels per millilitre (MBq/ml), gigabecquerels per millilitre (GBq/ml)

  • millibecquerels per litre (mBq/l), becquerels per litre (Bq/l), kilobecquerels per litre (kBq/l), megabecquerels per litre (MBq/l), gigabecquerels per litre (GBq/l)

  • millibecquerels per cubic metre (mBq/m³), becquerels per cubic metre (Bq/m³), kilobecquerels per cubic metre (kBq/m³), megabecquerels per cubic metre (MBq/m³), gigabecquerels per cubic metre (GBq/m³)

Legacy units (curie-based)

  • picocuries per millilitre (pCi/ml), nanocuries per millilitre (nCi/ml), microcuries per millilitre (µCi/ml), millicuries per millilitre (mCi/ml), curies per millilitre (Ci/ml)

  • picocuries per litre (pCi/l), nanocuries per litre (nCi/l), microcuries per litre (µCi/l), millicuries per litre (mCi/l), curies per litre (Ci/l)

  • picocuries per cubic metre (pCi/m³), nanocuries per cubic metre (nCi/m³), microcuries per cubic metre (µCi/m³), millicuries per cubic metre (mCi/m³), curies per cubic metre (Ci/m³)

Conversion basis

Conversions are based on the standard relationship:

1 Ci = 3.7 × 10¹⁰ Bq

Volume conversions are based on standard metric relationships:

  • 1 L = 1,000 mL

  • 1 m³ = 1,000 L = 1,000,000 mL

Appropriate use

This calculator is suitable for use when:

  • interpreting environmental and workplace monitoring results expressed in different volumetric units;

  • reviewing international publications where curie-based volume concentrations are used (e.g. pCi/L);

  • converting values for communication or comparison purposes;

  • supporting education and professional development activities.

It is not intended to replace sampling strategy, laboratory reporting requirements, uncertainty evaluation, or regulatory submissions where additional context is required.

Important note

The results provided by this calculator are indicative only and assume idealised unit relationships. They do not account for uncertainty, measurement methodology, sampling representativeness, or decay since reference time.

Outputs should not be relied upon as the sole basis for compliance decisions or safety justifications. Where required, advice should be sought from a competent Radiation Protection Adviser (RPA), Radioactive Waste Adviser (RWA) or other suitably qualified professional.

Related guidance

Activity concentration quantities and units are discussed within internationally recognised metrology and radiological protection guidance and are implemented across UK regulatory frameworks relevant to workplace monitoring, environmental monitoring, and discharges.

Users should ensure that activity concentration values are interpreted within their correct measurement, regulatory, and exposure context.

For advice on applying activity concentration information within your organisation or regulatory framework, please contact RP Alba Ltd.