What were ephahs, homers, shekels and gerahs? (Ezek 45:10-12)

You shall have just balances, a just ephah, and a just bath. 11 The ephah and the bath shall be of the same measure, the bath containing one tenth of a homer, and the ephah one tenth of a homer; the homer shall be the standard measure. 12 The shekel shall be twenty gerahs; twenty shekels plus twenty-five shekels plus fifteen shekels shall be your mina. (Ezekiel 45:10-12)

This passage is teaching that we should not use dishonest scales in business. When we sell things, we should use accurate measurements.

Each of the different words were measures of volume or weight. It can be difficult to determine precise modern equivalents, and while the following values are those usually quoted, they are only approximate.

• The bath was used to measure quantities of liquids (e.g., 2 Chronicles 2:10; Ezra 7:22; 1 Kings 7:26; Isaiah 5:10). One bath was about 22 liters or 6 gallons.
• An ephah was the equivalent dry measure (e.g., Exodus 16:36; 1 Samuel 17:17; Zechariah 5:6), also about 22 liters or 0.6 bushels.
• A homer was equivalent to ten baths or ten ephahs; that is 220 liters (6 bushels or 58 gallons).
• A shekel was a weight, equal to about 11.5 grams or 0.4 ounces.
• A gerah was the smallest measure of weight, equal to one twentieth of a shekel: 0.6 grams or 0.02 ounces.
• The mina seems to have varied in weight and was either 50 or 60 shekels depending on the country and time period. In this passage from Ezekiel (written in Babylon in about 580 BC), a mina is defined as 20+25+15=60 shekels. That is, it was equivalent to 0.7kg or 1.5 pounds.

A useful table of weights and measures is given here.