How the BTD Score Works

What is the BTD Score?

The BTD Score is BigToolDeals' own measure of how far a current deal's price is below that product's own price history. It is a BTD measure, not a retailer's rating and not a product rating.

The scale

• Current deals score between 50 and 99. A higher score means a bigger price drop.
• The score is not a percentage, and it isn't out of 100.
• 99 is the top of the scale. Any credited drop of about 33% or more scores 99, so several deals can share that score, and deals with similar drops can share a score too.
• A score of 50 means a very small credited drop.

How it's calculated

BTD Score = 50 + 1.5 × the credited drop, rounded down and capped at 99. The credited drop is how far today's price is below an average price, in percentage points. Which average is used depends on how much history the product has:

• Usually: the smaller of the drops against the product's 90-day and 365-day average prices. Using the smaller drop means a price that only looks low because the last few months were unusually high doesn't score as highly.
• When today's price is above its 365-day average: the smaller of the drops against its 90-day and 180-day averages, but only if the 180-day drop is at least 10%. Otherwise the deal gets no score.
• When no 365-day average is available yet: the drop against its 90-day average alone.

Each deal page says which comparison its score used. Percentages on BigToolDeals are shown as whole numbers, but the score is calculated from the exact, unrounded drop, so working the formula from the rounded percentage may give a score one point lower than the one shown.

Why it can differ from “% below its 90-day average”

Deal pages and cards also show how far the price is below its 90-day average. That figure is the 90-day comparison only. The score uses the smaller of the comparisons above, so the two numbers can differ.

Where the price history comes from

For Amazon deals, the price history is Amazon's, as recorded by Keepa, an independent price-tracking service. BigToolDeals isn't affiliated with or endorsed by Amazon or Keepa. Deals that don't have this kind of price history get no score: BTD never scores a deal against a list price alone.

What the score doesn't tell you

• It doesn't measure product quality, reliability or reviews.
• It doesn't rate the seller or tell you whether another product is better value.
• It doesn't guarantee the lowest price available anywhere, or that the price won't drop further.
• It isn't based on a manufacturer's list price or a retailer's advertised discount.

How often it changes

BTD recalculates the score each time it checks a deal, usually at least once a day, and prices can change between checks. Products need about 90 days of price history before they can become deals. When something is no longer a current deal, its page shows no score.

How to use it

Compare scores to see which deals are furthest below their own usual price, then check the current price, the product and the seller at the retailer before you buy. See also how BTD finds deals, the FAQ and our affiliate disclosure.