Techniques for estimating measurements

Bill Mollison apparently measured distances by his paces, which he had figured to the millimeter I think?

Every three steps I take is roughly the same as my height, and roughly the length of my tatami mats (though non-standard). That's still especially useful for me here in Japan since area is typically measured by tatami mats.

My index fingernail width is barely over 1 cm.

The length of my hand at its widest span is 20 cm in either direction.

Do you use any similar metrics for quick measurements when you may not have a ruler, tape, or other accurate measuring tools.

Perhaps some other method that doesn't involve body parts?

I'm pretty good at estimating distances just from measuring things so much.

My slightly exaggerated pace is 1 yard so that comes in handy.  

I do that a lot when I'm doing carpentry.  My index finger is 1.0" from the tip to the first joint, The span of my hand is 4", and my pace is 5'.  Those work out to be 2.5cm, 10cm, and 150cm.

If I were in a trade that required constant length measurements, I would seriously consider a ruler tattoo.

I've got all kinds of measurements figured out on various parts of my hands, in inches and centimeters.

I don't pace out distances all that often, so I have to figure out how many steps equals what every time I do a project that requires it. I should write it down somewhere and try to remember it. Our ground is so uneven that i find pacing it out is pretty inaccurate here anyway, though.

I found a thing online one time that had pictures of various things at various distances from the camera that was really helpful in estimating distances in the project I was working on that year.

I am pretty good at long distances. No real technique but a quarter mile, half mile, mile etc I am pretty accurate with.

I struggle a bit with forest acreages but open land I can pretty much guess the acreage accurately. By that I mean I can look at a field and say, “that is about a 12 acre field and be spot on”

It does seem like imperial units have an advantage over metric when estimating without a standardized measuring device. 1000 paces is about a mile, so 100 paces is 1/10th of a mile. An inch is roughly the distance between two knuckles on a finger, and a foot is, well, about the length of a foot.

Jordan Holland wrote:If I were in a trade that required constant length measurements, I would seriously consider a ruler tattoo.

Fellow Adam Savage fan? I've considered this, he sells a temporary tattoo of his tattooed ruler... in case anyone wants to test-drive the idea.

My thumb is 1" wide.
My  thumb  is 3" long (at 90*), 6" to the tip of middle finger, from thumb in that posture. 9" thumb tip to pinky tip while stretching all the way.
My foot (in my boot) is just over 12", it's okay for planting or a quick check rather than seeking a tape measure (especially if stepping off both the item and the space).
Elbow to tip of index finger is 18-1/4", close enough again to not go running for the tape measure.
I've never felt super confident about paces as a measurement, so don't practice it, and remain unsure.

Like Mike Hassl, I am constantly measuring at work, so I can size things up pretty well by eye.

There's also the factor of "measuring" versus "identifying" from a limited, known? set of measurements. Is this a 1/4"-20 bolt, or an M6 screw? Is it 2-1/2" long, or 3" long?
Is this dowel 5/16" or 3/8"? Is 10mm an option, then it just got trickier.

I always keep a small measuring tape in my pocket, plus I have a good feel of lengths between 1mm and 2 meters.
For larger distances I use my step which is 82 cm. It's extremely useful - without reaching for my 50 m measuring tape I can quickly and quite precisely measure distances in my garden, orchard, estimate the needed length of pipes, bulk materials, size of foundations, etc.