Cotco is a free Canadian cost-checking site: compare unit prices, look up barcodes, search recalls, and see what things have actually cost. Start here
Methodology
Every formula, written out
Nothing on Cotco is a black box. These are the exact calculations the tools run, the conversion factors they use, and the assumptions you should check before trusting a result.
Unit price
Unit price is price ÷ quantity, after both packages are converted to a shared base unit within the same dimension. Weight, volume, area, and count are treated as separate dimensions and are never compared against one another.
- Weight base unit: gram. 1 lb = 453.59237 g, 1 oz = 28.349523125 g, 1 kg = 1000 g.
- Volume base unit: millilitre. 1 L = 1000 mL, 1 imperial fl oz = 28.4130625 mL, 1 US fl oz = 29.5735295625 mL (shown only where a label uses it).
- Area base unit: square metre. 1 sq ft = 0.092903 sq m.
- Count base unit: one item.
Full precision is carried through the calculation; only the displayed figure is rounded. Per-unit prices are shown to enough decimal places to keep cheap staples distinguishable. Percentage differences use (higher − lower) ÷ higher, so "18% cheaper" means the cheaper option costs 18% less than the more expensive one.
Bulk buying break-even
Bulk savings are computed on usable quantity, not purchased quantity. Effective unit price is price ÷ (quantity × (1 − waste rate)). Waste rate is your estimate of the share you expect to spoil, expire, or discard. A bulk package wins only when its effective unit price is below the smaller package's effective unit price.
The break-even waste rate — the point where bulk stops being cheaper — is 1 − (bulk unit price ÷ small unit price) when the small package has no waste.
Cost per use
Cost per use is (purchase price + lifetime upkeep − expected resale value) ÷ expected uses. Upkeep covers consumables, maintenance, and repairs over the period you plan to own the item. Resale value is subtracted because it is money you expect to recover, not money spent. Two items are only comparable when the use count is defined the same way for both.
Membership break-even
A paid membership breaks even when annual savings equal the annual fee: break-even spend = annual fee ÷ savings rate. Where a membership also returns a rebate percentage, the combined rate is used. Trips per year and average basket size convert that break-even spend into a realistic yearly total so you can see whether your actual shopping volume clears the bar.
Price trends
Trend pages plot published index or average-price values exactly as the source reports them; Cotco does not smooth, seasonally adjust, or re-base the series. Change figures are simple period-over-period percentage changes between the latest value and the value 12 or 60 months earlier. A national series is not a local price and should be read as direction, not as what you will pay.
Product and recall data
Product records are shown as published by the community database that supplies them, including missing or stale fields. Recall results link to the official government notice, which is always the authoritative version. Absence of a result is not proof that no recall exists.
Rounding and display conventions
- Currency is rounded to cents for totals and shown with extra precision for per-unit figures.
- Percentages are shown to one decimal place.
- Numeric results use a monospaced figure style so digits align in comparisons.
- Inputs that are blank or non-numeric produce no result rather than a zero.
Cotco's calculators are decision aids, not financial advice. Results depend entirely on the inputs you supply, including estimates such as waste rate, expected uses, and resale value.