Unit Prices: Comparing Packs of Different Sizes

How to compare products sold in different sizes by working out the price per gram, litre or piece, and why bigger isn't always cheaper.

Is a 500 gram pack for 120 rupees cheaper than a 1 kilogram pack for 220 rupees? Comparing unit prices answers such questions quickly.

Calculating unit price

Unit price = Pack price / Quantity

500 g for 120 rupees = 120 / 0.5 kg = 240 rupees per kg.
1 kg for 220 rupees = 220 rupees per kg.

The larger pack is cheaper per kilogram.

Choose a consistent unit

Convert to the same unit: per kilogram, per 100 grams, per litre or per piece. For detergents, some compare per wash; for tablets, per dose.

Legal help

In India, the Legal Metrology (Packaged Commodities) Rules require packaged goods to display the unit sale price, such as price per kilogram or litre, alongside the maximum retail price. Check the label for it.

Bigger isn’t always cheaper

Some large packs cost more per unit than smaller ones, especially during promotions on smaller sizes.
Offers like “20 percent extra” may still be more expensive per unit than a rival brand.
Shrinkflation: packs may shrink while prices stay the same, raising unit prices.

Other things to consider

Waste: a large pack is only cheaper if you use it before it spoils.
Storage: space at home matters.
Cash flow: buying in bulk needs more money upfront.
Quality: a cheaper unit price for a lower-quality product may not be a bargain.

Quick mental maths

To compare 400 g for 90 rupees with 1 kg for 210 rupees: 400 g x 2.5 = 1 kg, and 90 x 2.5 = 225 rupees. So the 1 kg pack is cheaper.
Rounding makes comparisons fast in the shop.

The shampoo shelf

A shopper compares shampoo: 180 ml for 160 rupees, 340 ml for 290 rupees and a "value pack" of 650 ml for 575 rupees. Per 100 ml, they cost about 89, 85 and 88 rupees. The middle size is actually the best deal.

Thinking the family pack is always the best value

Unit prices vary, and promotions on smaller packs can make them cheaper. Always compare price per unit.

Key takeaways

Unit price is the pack price divided by quantity.
Convert to the same unit, such as per kg or per 100 ml.
Indian packaging rules require a unit sale price on labels.
Bigger packs aren't always cheaper, and waste matters too.