Estimate baby formula cost by feeding amount.
Formula is priced per tin but consumed per millilitre of made-up feed, so the two have to be bridged by the powder concentration — around 13 grams per 100 ml for most first infant formulas. Convert the daily feed volume into grams of powder, scale by the number of days, and divide by tin weight to get tins rather than guessing packs. The cost-per-day figure is what makes brands genuinely comparable, because tin sizes differ enough that shelf prices tell you very little.
Infant formula cost
Daily powder = daily ml / 100 x grams per 100 ml; tins = daily powder x days / grams per tin; cost = tins x price
Cost estimates only, not infant feeding advice. Always prepare formula exactly as the manufacturer's instructions specify, and discuss feeding volumes and any change of formula with your health visitor, midwife or paediatrician.
Roughly 150 ml per kilogram of body weight per day for the first months, so about 750-800 ml for a 5 kg baby. Volume rises with weight and then falls as solids are introduced from around six months.
For purchasing, yes — you cannot buy a fraction of a tin, and running out mid-week means paying convenience-store prices. The fractional figure here is the true consumption, which is the right basis for cost comparison.
Infant formula composition is tightly regulated, so nutritional requirements are met across brands regardless of price. Differences are in optional added ingredients and in how well a particular baby tolerates a specific formulation.