The Leverhulme Research Centre for Forensic Science Measurement Uncertainty Calculator (MUCalc) is an application for calculating measurement uncertainty in accordance with the standards of International Organization for Standardization ISO/IEC 17025. This version (v3.0.0) of the software computes uncertainty components for Homogeneity, Method Precision, Standard Solution, Sample Volume and Calibration Curve with the Calibration Curve assumed to be linear. If data is uploaded for all components, the Combined Uncertainty is computed using all components. An uncertainty component can be excluded from the Combined Uncertainty by simply not uploading any data for that component. Once data is uploaded, a step by step computation and details of all formulas used can be accessed by clicking on the respective uncertainty component tab displayed at the left hand side of the screen. Each uncertainty component has three main tabs; Overview, Method and Step by Step Calculations. Together these give more detailed information about the approach used. Version 3.0.0 of the MUCalc newly includes a Homogeneity Test, to test whether a substance is homogenous. A live version of this application can be viewed at: https://uod.ac.uk/lrcfsmucalc