Yes. A student is allowed to use a very basic onscreen calculator on the DM (Decision Making) and QR (Quantitative Reasoning) subtests of the UCAT to answer questions.
It has to be noted that the onscreen calculator provided is very basic and different from most other calculators the student may have used in school. Hence, the student is advised to get familiar with the UCAT onscreen calculator at least a month before taking the UCAT.
You may click on https://www.ucattools.com/ucat-calculator/ to understand what the UCAT calculator looks like.
However, we recommend taking the official mock UCAT tests available for free on the official UCAT website designed and maintained by Pearson Vue, to get to experience the UCAT calculator first-hand.
The same can be found at https://www.ucat.ac.uk/prepare/practice-tests/