Danyk.cz offers free online calculators designed to help with physics and everyday calculations. Its density calculator works with the relationship between mass, volume, and density: enter any two values to calculate the third. Users can select from a range of metric mass and volume units, including grams, kilograms, liters, and cubic meters, and choose among density units such as grams or kilograms per cubic meter. The calculator also supports automatic or user-selected metric prefixes and convenient adjustment controls for changing values.

To support practical comparisons, the page provides reference density lists for common gases, liquids, and solids, alongside collections of frequently used mass and volume values. The site also features other basic physics calculations, including a water-heating-time calculator. Danyk.cz describes its tools as intended for reference and cautions that results are not guaranteed to be correct, advising users to rely on them at their own risk. Its pages include information about the site, contact details, and a privacy policy.