Track grocery prices and measure your own kitchen inflation

Groceries are the largest flexible expense in most homes, and the hardest to judge. Prices change a little every week, pack sizes shrink quietly, and nobody remembers what dal cost in January. A small amount of record-keeping fixes that.

Compare by unit price, not pack price

A 5 kg bag at ₹340 and a 2 kg bag at ₹150 cannot be compared until you divide. The first is ₹68 a kilo and the second is ₹75. Unit price, per kilo or per litre, is the only number that lets you compare across pack sizes, brands and shops.

It also exposes two common tricks. Larger packs are not always cheaper per kilo, particularly during promotions on the smaller size. And when a pack goes from 1 kg to 900 g at the same price, the unit price has risen by about 11% even though the price tag has not moved.

Record a short list, not everything

You do not need to track every item. A short list of staples makes up a large part of most grocery bills: rice, atta, dals, cooking oil, milk, sugar, tea or coffee, eggs, onions, potatoes, tomatoes and a few more. For each purchase, note four things: the item, the quantity, the price paid and the shop. That takes seconds at the counter and is enough for everything that follows.

Find out which shop is actually cheaper

Most people have a feeling about which shop is cheap. The records often disagree. A supermarket may be cheaper for packaged staples and dearer for vegetables. The neighbourhood shop may match prices on rice and oil and save you a trip. After a month or two of records you can see, per item, where the lowest unit price was, and split your shopping accordingly.

Count the whole cost. A saving of ₹60 that needs a ₹90 auto ride is not a saving, and neither is a bulk pack that goes stale before you finish it.

Know when things run out

If you note the date you opened a 10 kg bag of rice and the date it finished, you know your household's rate of use. From then on you can tell in advance when the next bag is needed. That matters for the budget, because an emergency top-up from the nearest shop often costs more.

Work out your own inflation

The official inflation figure, the Consumer Price Index, is worked out from a fixed national basket of goods and services, weighted using a survey of household spending. Your basket is different. To measure yours:

1. Write down what your household uses in a typical month: for example 10 kg rice, 5 kg atta, 3 litres oil, 30 litres milk, 2 kg toor dal.
2. Price that fixed basket at the unit prices you paid in an earlier month.
3. Price the same basket at this month's unit prices.
4. The difference, as a percentage of the earlier total, is your kitchen inflation.

Keeping the quantities fixed is the important part. If you simply compare grocery bills, you cannot tell whether you spent more because prices rose or because you bought more.

What to do with the numbers

• Raise the grocery line in your budget by what the basket shows, rather than guessing.
• Stock up on non-perishables when the unit price is well below your usual, and only to the extent you will use them.
• Look at the two or three items with the largest increase and see whether another brand, pack size or shop brings them back down.