Weights

The Logic of Harappan Weights

The Harappans used a precise, regulated system of weights to control exchange — both local trade and long-distance commerce. This system was not arbitrary; it followed a dual pattern that combined two number systems.

Why two systems?

• Lower denominations (small weights) followed a binary pattern — each weight is double the previous.
• Higher denominations (larger weights) followed a decimal pattern — multiples of 10.

This design allowed flexibility: small weights for fine items (like jewellery and beads), larger weights for bulk goods.

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The Weight System in Detail

Material and shape:

• Made of chert (a hard stone).
• Usually cubical (cube-shaped).
• No markings — the value was determined purely by mass, not by any inscription.

Lower denominations (binary series):

The smallest weights doubled at each step:

Each weight is exactly twice the previous one. This is a binary progression (powers of 2).

Higher denominations (decimal series):

After 32, the pattern switched to multiples of 10:

Notice:

• 160 = 32 × 5 (but the jump is not simply 5× — the system shifts to decimal).
• 200 = 2 × 100, 320 = 2 × 160, 640 = 2 × 320, etc. So the higher weights follow a decimal base (multiples of 10, 100, etc.), but still double within that base.

Why this dual system?

• Binary weights are efficient for small, precise measurements (e.g., gold dust, beads).
• Decimal weights are convenient for larger quantities (e.g., grain, metal ingots).
• The switch at 32 suggests that 32 was the largest "small" weight — beyond that, decimal became more practical.

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Practical Use …