How to Actually Track Your Grocery Inflation Rate

The national inflation number you see on the news is a weighted average across hundreds of product categories, adjusted for a hypothetical average household. It probably doesn't describe your life.

If you drink three cups of coffee a day and eat red meat twice a week, your personal inflation rate might be double the headline number right now. If you mostly eat rice, lentils, and frozen vegetables, it might be half.

The only way to know is to measure it yourself.

What "personal inflation rate" actually means

Your personal inflation rate is the percentage change in what you pay for the goods you actually purchase, compared to what you paid for those same goods in a previous period.

The key phrase is the goods you actually purchase. Not a standardized basket. Not national averages. Your stuff, at your stores, over your timeline.

Method 1: The manual way (spreadsheet)

This works. It's tedious, but it works.

1. Start a log. Every time you shop, record the item name, the package size, the price, and the date. You need size to calculate unit price.
2. Calculate unit prices. Always work in price per 100g, per litre, or per unit — not sticker price. A $4.99 bag of chips that shrank from 250g to 220g is not the same price as it was.
3. Compare the same item over time. After 2–3 months, you can start calculating percentage changes on your most-purchased items.
4. Weight by purchase frequency. Items you buy weekly count more than items you buy once a month. A simple way: multiply the price change by how many times you buy it per month, then average across all items.

The result is your personal inflation rate for the period measured.

Method 2: Scan your receipts

This is the same process, automated. When you scan a receipt, Ghostflation extracts every item, normalizes the name and size, and builds a price history. After a few months of scans:

• - Your Personal Inflation Rate is calculated automatically, weighted by your actual purchase frequency
• - Shrinkflation flags appear when we detect the same product at a smaller size
• - Category breakdowns show which parts of your basket are rising fastest

The math is identical to the spreadsheet method — it's just done for you.

What to do with the number

Once you know your personal inflation rate, you can act on it:

• - If it's higher than the CPI: Your basket is in a category getting hit hard. Look at what's driving it — usually one or two categories (meat, dairy, coffee) explain most of the gap.
• - Compare across stores: Maybe the items driving your inflation are cheaper elsewhere. Price differences of 15–25% on the same item across stores are common in Canada.
• - Substitute within category: If beef is up 20%, chicken thighs are not. If name-brand pasta is up 30%, the store brand usually isn't.
• - Time your purchases: Many items have predictable sale cycles. If you know ground beef goes on sale every 3 weeks at your Superstore, you can stock up then.

The number that matters

The national CPI has its uses — it guides interest rate policy, wage negotiations, economic planning. But for your household, it's a blurry average that may have almost nothing to do with what you're actually experiencing at checkout.

Your personal inflation rate is the number that tells the truth about what's happening to your money. It's worth knowing.