Methods & sources

Prices

Once a day our collector makes one request per store to its public product feed (the standard Shopify /products.json listing, up to 250 products), identifying itself as DoomsdayDealsBot/1.0 (+https://doomsdaydeals.pages.dev/about/; once-daily price check). We store each day's prices in a dated file. "Price today" is the lowest in-stock price among a product's sizes or options. Stores with more than 250 products are only partly covered for now.

Cost per day and per gallon

Bunker Index: price ÷ (total calories ÷ 2,000). Calories must appear on the brand's product page as a total, as calories per pouch for a single-pouch product, or as calories per day for a kit with a day count in its name. We quote the exact words and link the page. If none of those appear, the product shows "not listed" and isn't ranked. Products sold in several sizes at different prices aren't ranked, because the calorie total may apply to only one size.

Water Index: price ÷ the brand's rated capacity in gallons. When a system has parts with different ratings, we use the shortest-lived part and say so. Liters are converted at 3.785 per gallon.

Deal Meter

Today's price vs. the median of that product's daily lowest price over up to 90 days. "Unusually low" is 15% or more below the median, "above usual" is 5% or more above, and "fake sale?" flags a brand "compare at" price on a product whose price hasn't moved in 30+ days. No verdict before 14 days of history.

Shelf life

Quoted from the brand's product page, with the claim type ("up to", taste guarantee, stated). We don't test products and don't extend or shorten anyone's claim.

Stores included and skipped

Before adding a store we read its robots.txt and terms of service (checked Oct 17, 2026). If the terms forbid scraping, crawling, robots or automated access, we skip the store, even when the feed is technically public.

What we don't do

• No Amazon prices (we aren't eligible for Amazon's price API).
• No logins, no carts, no checkout automation.
• No made-up numbers: if a brand doesn't list it, we say "not listed".
• No paid placement inside rankings, ever.