Why shelf prices mislead you
Formula tins are not a standard size. Walk down the baby aisle and you'll find 700g, 800g and 900g tins sitting alongside each other at prices that look broadly similar. The tin that looks cheapest is frequently the smallest.
The fix is one piece of arithmetic: divide the price by the weight, then multiply to get a price per 100g. A £11.50 tin of 800g works out at £1.44 per 100g. A £10.50 tin of 700g looks cheaper on the shelf but is £1.50 per 100g. The 'cheaper' tin costs you more.
Price per 100g is the only formula number worth comparing. Everything else is packaging.
Turning price per 100g into price per feed
Most first infant formulas use a scoop of roughly 4.3g of powder per 30ml of water, though this varies by brand — always follow the instructions on your specific tin.
If you want a per-feed figure, work out how many grams your baby's usual bottle takes, then multiply by your price per gram. It's a more useful number than the tin price when you're deciding whether to switch brands, because it tells you what a real day actually costs.
Cheaper formula is not worse formula
First infant formula sold in the UK has to meet compositional standards set in law. Every product on the shelf must provide the nutrition an infant needs for the first months of life. That's why the NHS and Britain's competition authority have both pointed out that price differences between brands do not reflect differences in how well the formula meets a baby's nutritional needs.
Differences between brands come down to optional added ingredients, marketing and brand positioning. If your baby is settled on a formula, there's no need to change. But if you're choosing for the first time, a higher price is not evidence of a better feed.
Why you never see formula in a sale
UK regulations restrict how first infant formula can be sold. It can't be advertised to the public, can't be included in promotions or multibuys, can't be price-matched, and generally can't earn loyalty points or be paid for with vouchers. Retailers apply these rules themselves, which is why formula is often excluded at the checkout.
The practical consequence: you can't wait for a deal on first infant formula. The only saving available to you is finding a retailer whose everyday price per 100g is lower. That's exactly the comparison ParentPrice runs.
- No discounts, no multibuys, no loyalty points on first infant formula.
- Follow-on milk and toddler milks are treated differently and can be promoted.
- Everyday price differences between retailers are real and are where the saving is.
Powder, liquid and 'ready to feed'
Ready-to-feed cartons and bottles are pre-mixed and sterile, which is genuinely useful when travelling or in the middle of the night. They also cost substantially more per feed than making up powder.
Compare them honestly: work out what a single feed costs in each format. If ready-to-feed is worth the convenience to you, that's a fair choice — just make it knowing what the convenience costs rather than assuming the shelf price tells you.
A quick comparison routine
- Note the price and the tin weight for each option.
- Work out price per 100g for each: (price ÷ grams) × 100.
- Compare like with like — first infant formula against first infant formula.
- Check delivery. A lower online price with £4.95 postage is often not a saving on a single tin.
- Check the expiry date if you're buying several tins at once.