In everyday life digits are especially interesting as it’s not abstract numbers, but for practical units: Euro, dollar, degrees, kilograms, liters, meters, minute, Watt...
Usually those are, like the decimal number system, also named in multiples of ten.
The SI (Système International (d' Unites)) appoints these multiples, so everyone knows kilo-meter is 1,000 meters. Every preposition appoints a standard 10 -fold, useful for various units (volume, surface area, pressure, energy, temperature...)

Storage for computer has made everyone acquainted with great values ​​. Development and production of very small miniature devices, nanotechnology also teaches smaller than micro - thinking.

10n Prefix Symbol Name Decimal

Weight, volume, distance, time and temperature are the most commonly used units in our daily lives.
For all units is officially determined how big they are, and / or how they are determined or measured.
Identifying and using standards is based on accordance, there are no "natural” units located presenting themselves. Attempts in the past, such as (width) an inch, the (length of a strengthened) ell (arm), the weight of a grain (grain), a foot... do not provide exact measurements.
Were our units of measurement lost, we would therefore have to meet and capture new.

One hectare (ha) is 100 x 100 = 10.000m².
1 km² = 1000x1000 m and 1 ha = 100x100m, so 1km² = 100ha or 1ha = 0.01km².

Dimensions and distances were previously based on body parts or performance. They are never exact, and vary by region and body size.
A thumb is between 2.4 and 2.7 cm. The English thumb or inch is 25.4 mm (or 2.54 cm)
One foot is 12 inches or 304.8 mm = 0.3048 m. A meter is therefore 1 / 0,3048 or about 3.28 feet.
A span the distance between the thumb and little finger of an outstretched hand, about 20 cm.
Hand (palm) and fist approximately 10 cm?
A ell is an ancient measure of length taken straight from fingertip to elbow approximately (68.2 -) 69.4 cm.
A pass is 2 1/2 feet.
A fathom is the distance between the fingertips with arms extended laterally. Usually, one fathom is rounded to 6 feet (180 cm). Mainly used to measure depths.
In a few steps, and a stone's throw anyone can imagine anything. But no one knows exactly how far it is.
Within walking distance is less than 1 km, an hour's walk is 5 to 6 km.
A day (march) is since the Romans between 30 and 50 km (military term).

Everywhere is within walking distance if you have the time.

In many cultures a grain was used as a small unit of weight. But which may, of course, also vary considerably. Which gives enormous differences for heavier weights.

Also a drop is no uniform measure of capacity. Depending on composition, temperature, drip shape (or opening), surface tension, etc. they vary for water of about 10 to about 50 micro liters. It is often assumed of 0.05 milliliters / drop.

I saw a video (Ancient History genre) claiming that the ancient Egyptians already knew a universal unit of measurement: a drop of water that was placed on an impenetrable surface always had a diameter of exactly one centimeter. With a ten multiples you automatically make a decimeter, a meter, ... And that corresponded to a (royal) leg (1 m), hand and thumb. Unfortunately, the basic assumption is already wrong: two drops can differ by a factor of 5 (by composition, temperature, etc.).

If you make a disc of 1 meter in diameter and put a ribbon around it, you will get the ratio pi, that is 314 cm.

1 / 6th of this circumference (pi) is 52.36 (royal el?). This is also the volume ratio (%) of a sphere (of 1 meter diameter for example) with a cube (rib 1 m).

In America and England are in practice still other and different systems used. A pound (lb) can be 500, 480, 433, 454 grams!
(Lb stands for libra, an abbreviation of the Latin Libra Pondo (libra: balance, for the constellation; Pondo: weight, recognizable in 'pounds').
Previously, there were regional differences everywhere (a roe, acre,...)! There were many more than two sizes and two weights to count. Not exactly practical and honest.

Late 19th and early 20th century dimensions were laid down by law, and they went standards and also calibrated: compared to an appropriate scale; and marked.
The Sumerians calibrated theire (stone and metal) weights already with a royal insignia.

Handy is the (approximate) agreement by use of (pure) water (4°C):
1,000 cm³ » 1.000 grams » 1,000 milliliters.
The weight is the product of the specific weight and the volume. A liter of water weighs 0,998 kg according to current standards.

In kitchen terms following measures are adopted in grams of water: a teaspoon: 4.5 gr, tablespoon: 12 gr. And a normally filled cup or wine glass: 125gr, a beer glass, normally filled 250 and 330 grams.

Also, springs can be used to weigh. (Both tensile, compressive and spiral- or torsion springs.) Spring balances are especially known to weigh luggage or fish. They exist by caliber, ex. to 5 grams, 500 grams, even up to 100 kg. For laboratory applications, there are very exact copies.

A bascule is a scale with a long rod with a central pivot. At both ends hangs a container. In one container, the object to be weighed is placed in equilibrium with the other containing weights in the scales.
For heavier objects and animals a bascule was used with an arm and corresponding weight ratio of 1 to 10 on the rod.
The Romans already had precision scales, the Stratera, with a sliding weight on a unequal yoke with a scale.

Binas is an interesting vademecum for natural sciences in college and high school with a clear overview of tables, charts, formulas and illustrations for physics, chemistry, biology and mathematics. Worth to have it in your library to look up more.