Perhaps you can't measure the present. You can define it as neither the future nor the past, a tiny tiny spot that only calculus or philosophy can deal with! Oh no! Your question is already too difficult to answer!
Memory is the key I think and it's very difficult to measure memory! These concepts - measurement of space, of being - are inventions by humans, much like the grammar of language is an invention. We don't really need time (and grammar!) but they are crucial to our survival in our present situation.
The present must be a timeless place, where the future is a seed and the past already grown and gone!
If you for example shout your name into a canyon and listen to the echo you'll know that those echoes are from the past because the original shout has gone. Are the echoes still part of the present? No. They are sort of phantoms of the future.
Your memory allows you to put things into perspective and if it's working properly gives us the ability to work with time.
Very old people with severe dementia for example have no concept of time and can mistake the past for the present - my old mother does it. I think she exists in a continuous kind of present?
If we spoke or thought very slowly perhaps the present would be stretchable? As things stand, I don't think the present can be measured but I'm certain some scientist out there has tried to do just that!