How we score a deal.

01 / PrincipleA discount alone is not a deal.

An Amazon listing showing "50% off" tells you almost nothing. It might be off an invented RRP. It might match a price the product has sold at for six months. It might disappear in two hours, replaced by something worse. The number on the page is the easiest input to manipulate.

Our score asks a different question: across every signal we can verify, how strong is the case for buying this product today? Discount magnitude matters. So does where this price sits in the product's own history, whether stock is real, whether the seller is reliable, and whether the category is one where deep cuts are rare or routine.

The score is a single number, but it's the aggregate of those five readings. If any one of them is weak, the score drops.

02 / Five inputsWhat we measure.

1. Discount magnitude — 35%

How far below the reference price the product currently sits. The reference is the product's own typical high — the 90th percentile of its recorded daily prices over the trailing 365 days — so a one-day marketplace spike or an inflated manufacturer RRP can't move it. Where we hold a genuine RRP that's lower than the recorded typical high, we use that instead: the claimed price can only ever shrink a discount, never inflate one. Linear up to 60% off — beyond that the score saturates, because a 70%-off claim usually means something else is wrong. We also require the current price to sit meaningfully below the product's median price: an item selling at its normal everyday price is not a deal, however large the gap to some recorded high.

2. History confidence — 20%

How many distinct daily price snapshots we hold for this ASIN. More history means we can be more confident the price drop is unusual. A deal on a product we've tracked for 547 days outscores the same drop on a product we first saw last week — because we know more about the baseline.

3. Popularity — 15%

Where the product sits in its category's sales rank. Top-decile sellers earn the full weight. We're not trying to surface forgotten oddities — if nobody buys it, it's not the deal of the day, however cheap it is.

4. Availability — 15%

Two binary checks. Is it in stock right now? Is it sold and dispatched by Amazon directly? Third-party sellers can vanish, ship slowly, or price-gouge — penalising them keeps the feed practical for readers who will actually click through.

5. Category quality — 10%

An editorial multiplier per category. Tech and kitchen score higher because deep discounts in those categories are usually tied to real product cycles. Books and toys score lower — fake markdowns are endemic. The multipliers are visible below and we publish changes in the changelog.

All-time low bonus — 5%

If today's price is the lowest we've ever recorded for the product, we add up to 5 points. Not because all-time lows are automatically buys — but because they're informationally valuable for readers running their own decision.

03 / Weights & mathsThe actual formula.

Each input is normalised to a 0–1 range, then multiplied by its weight. The final score is the rounded sum, capped at 100.

score = round(
    clamp(discount_pct / 60, 0, 1) * 35
  + clamp(days_tracked / 365, 0, 1) * 20
  + clamp(popularity_pct / 100, 0, 1) * 15
  + ((in_stock ? 0.6 : 0) + (sold_by_amazon ? 0.4 : 0)) * 15
  + clamp(category_multiplier, 0, 1) * 10
  + (is_all_time_low ? 1 : 0) * 5
)

Category multipliers

Grade bands

We translate the numeric score into a four-tier grade for readability:

• Exceptional — 90 to 100. Top-decile signal across all inputs.
• Strong — 75 to 89. Above average, worth a look.
• Fair — 55 to 74. Decent discount, weaker supporting signals.
• Weak — below 55. Published rarely, mostly for transparency.

04 / A worked exampleSony WH-1000XM5 at £179.

Take a real deal from our seed catalogue: Sony WH-1000XM5 headphones, RRP £389, current price £179, sold by Amazon, in stock, with 547 days of price history showing this is the all-time low.

A score of 95 puts this deal in the top decile of everything we've published this quarter. The high reading isn't just the discount — it's the combination of a deep cut, a long history we can compare it against, and clean availability signals. Strip any one of those and the score lands meaningfully lower.

05 / Anti-junk filtersThings we will not publish.

Score is the headline, but it's not the only gate. Before a candidate is published, it must pass these checks:

• Minimum reviews. Listings with fewer than 50 verified reviews are deprioritised, and brand-new SKUs with almost no review history are held back by default.
• Review quality. Listings averaging below 3.8 stars are held back by default.
• Seller stability. ASINs sold by third-party sellers with under 95% positive feedback are excluded by default.
• Banned categories. No supplements, no weight-loss products, no anything age-restricted, no anything we wouldn't link our own family to.
• Suppression list. A small set of brands and ASINs editorially blocked because of historic price-gouging or quality complaints. The list is reviewed quarterly.
• Discount realism. The % off is always measured against the product's own verified price history — its RRP, or the highest price we've actually recorded — never an invented marketing "RRP". A big headline discount only shows when the higher price is real.

06 / OversightWhere the desk comes in.

Publishing is automated. Any candidate that clears the score threshold and the anti-junk filters above goes live — we don't hand-approve them one by one. A transparent, fully documented score is the point: it shouldn't need a gatekeeper to be trusted.

What the desk does is watch the live feed. We can pull or expire a deal at any time — if a price moves, stock runs out, or something looks off — usually within minutes of verifying the problem. Spot something wrong before we do? Tell us and we'll fix it the day we confirm it.

We do not accept payment from brands or sellers for placement. Our affiliate revenue comes from Amazon when you click through and buy. The score has no input from the affiliate commission rate.

07 / ChangelogWhat's changed.

Every revision of this algorithm is logged here in plain English.

Version 1.3 — 2 July 2026

• Reference price hardened: now the product's own typical high (90th percentile of the trailing year of recorded daily prices), never a claimed list price. A genuine RRP can only lower the reference, never raise it.
• New publish gate: the current price must sit meaningfully below the product's median price — items selling at their normal price no longer qualify as deals, regardless of any recorded spike.
• New publish gate: a minimum of 14 days of recorded history before we'll make any discount claim.
• Live deals are re-checked against these rules on every price sweep, so anything published under the old reference logic corrects or expires automatically.

Version 1.2 — 7 June 2026

• Discount-magnitude saturation lowered from 70% to 60% after six months of data.
• History-confidence cap raised from 180 days to 365 days.
• Discount % is now always measured against our own recorded price history, so a headline markdown can't be inflated by an invented RRP.

Version 1.1 — 14 March 2026

• Sold-by-Amazon weighting introduced inside the availability factor.
• Category multiplier table rebalanced after Q1 click-through analysis.

Version 1.0 — 12 December 2025

• Launch.