The calculation of UV indices requires some effort.
Because different wavelengths of UV radiation have different affectseffects on skin, to calculate the UV index you need to apply "McKinlay-Diffey" weighting factors to various wavelength components of UV radiation and then integrate (sum) those results and then divide by 25.
The procedure does not use ozone readings but it does use elevation and cloud cover.
The following two references list the procedure required:
