If you’d like to read more about diffraction from a technical perspective, there is an approachable explanation at cambridgecolour.com which discusses diffraction in the context of depth of field. A depth of field calculator is provided.
We think it’s a waste of time to bother with a depth of field calculator, which calculates based on ideal lenses, which don’t exist. Calculations can be misleading to anyone but experts; real-world factors intrude and make the calculation non-actionable when actual photos are taken with real lenses. Reasons for this include varying performance across the image area, curvature of field, astigmatism, spherical aberration, color aberrations, and the critical loss of contrast due to diffraction and other factors. Not to mention focus error in placing the ideal plane of focus. Know thine own lens(es), lest ye be misled!