Sheafase compares the prices and quantities you enter. It does not look up prices, and its results are only as accurate as what you type in. Every comparison follows the rules below.
Each product is compared by what it costs for the amount you receive, brought to one common unit: per litre for volume, per kilogram for weight, per metre for length, and per item, serving or use for counts. A 330 ml bottle and a 2 l bottle are compared per litre, and 100 g and 1 lb per kilogram. Products measured in different kinds of unit, such as weight and volume, cannot be compared with each other.
You choose what the amount means: the whole amount, the usable or drained amount, the yield, servings or uses.
Price to pay now is what you hand over at the till: the goods after offers and coupons, plus delivery, other charges, any tax added on top, and deposits.
Effective cost is the price to pay now minus refundable deposits and cashback you are due back, and never below zero. Value for money is ranked on effective cost. A Budget limit is checked against the price to pay now, because cashback and deposit refunds arrive after you have paid.
A product's offer is applied first: a percentage or fixed amount off, buy X get Y free, buy X get Y at a discount, or several packs for one price. Then its own coupon, then the order voucher, then delivery and tax. Free items count in the amount you receive.
A product with a multi-buy offer is compared at the smallest purchase that completes the offer once. Others are compared at their smallest purchase allowed. A voucher or free-delivery threshold that this purchase does not reach is not applied.
Check a Deal compares your deal with one other product, bought to match the deal's amount. A product that can be bought in exactly that amount is chosen first, then the best value at that amount, then the lower price to pay now. When no product can match the amount exactly, the smallest purchase that covers it is used, and the result says how much more that gives. At the same amount the two prices to pay now are like for like, so the difference between them is stated. When the amounts differ, the prices pay for different quantities, so the verdict compares value per unit instead.
Target Quantity and Budget look for combinations of whole packs, in the steps each product is sold in, within any stock limits you set. For exactly the amount you need, Target Quantity finds the lowest effective cost; for at least that amount, the lowest effective cost and then the least extra; for at most, the closest to the amount without going over, and then the lowest effective cost. Budget finds the most quantity or yield within your budget, then the lowest price to pay now, then the fewest packs and products.
Two products have the same value only when their prices per unit are exactly equal. Products within 0.5% of each other (the current margin) are marked as nearly the same, but keep their order.
When the value is exactly equal, the product needing fewer packs comes first, then the one with the lower price to pay now. The result names the rule that decided. Products equal on all three share a place: a full tie, not a narrow win. Tied combinations in Target Quantity and Budget are counted, and up to 12 are listed.
The pricing rules round final money amounts, such as the price to pay now, to the currency's smallest unit, with halves rounded away from zero. That rounding is part of the calculation.
Products are then compared exactly on those amounts and the quantities received: prices per unit are compared without dividing or rounding again.
The prices per unit, differences and percentages you see are worked out from those exact values and rounded once, for display only: prices per unit and differences to 2 decimal places, percentages to 1, with halves rounded away from zero. Each is marked ≈ when rounding changed it. A displayed figure never changes a ranking.
A real difference too small to show is never written as zero. A money amount that would round to 0.00 is shown as < 0.01, and a percentage that would round to 0.0% as < 0.1%. A percentage difference is a share of the next best product's price per unit.
A difference in price per unit compares value. It is not the amount you would save on any one purchase, because the packs hold different amounts.
Compare Products ranks each product at one purchase, as described above. It does not search other quantities, so the winner is not necessarily the best buy at every amount.
Target Quantity and Budget search within a fixed limit. If the limit is reached before every shopping plan has been checked, the result says so, and a better plan may exist beyond it. They show first place and up to two places below it. Over-budget alternatives come from a separate, smaller search that does not look for every possibility.