It would be ridiculous to measure the table you work at in miles.
You would never tell a friend that your thesis draft is coming along nicely at 972,638 characters.
And you wouldn’t record how many cups of coffee you had had to determine if you’d been working hard.
Units of measurement have to be fit for purpose. They have to be reasonable. And yet I’ve met many PhD candidates who measure themselves against other people. They doubt their success because they compare their research with a colleague’s work. They worry about their viva because they look at what their examiners have achieved and feel small.
How long have you been working on your PhD? How much have you done? What is your contribution? Responding to these questions is an appropriate measurement. You don’t need to compare yourself to others.
Measure yourself and see that you’re good enough in your own terms.