Let me demonstrate one of the best qualities of a good lens or glass, as we sometime refer to that integral part of the probably most important photographic equipment.
The DoF, or the Depth of Field, or simply said the part of the photo "on focus", depends on many parameters.
Yes, there is math and formula in and about that and yes, there are plenty of free and paid apps on all the mobile stores to give you the exact numbers.
You are kindly invited and more than welcome to join "The Photographic Society" Community on HIVE here: 
Some of my favorite photographs and digital art, along with some of my recent visuals, all in the highest resolution and quality, are all available for licensing inside my searchable portfolio at Alamy: https://www.alamy.com/portfolio/112427.html
Are you a fan of NFTs? Check out my portfolio while some of my best photographs and digital art are still on sale: https://opensea.io/LightCaptured
Check out some of my visuals available in high resolution, you could get a license here for publicly utilizing my works, all approved by the quality review team of Adobe, Inc.: https://stock.adobe.com/contributor/206416265/lightcaptured
Copyright: Light Captured
All the photographs, digital art and text in my posts, unless specified otherwise, are my own property and created by me.
For licensing my photos, please contact me!
I wish you one great day; stay safe, stay strong and let your muse be always on your shoulder!
The divider I use in my posts I have created in Adobe Express.
