CartrouteHow does Cartroute decide which retailer is cheapest?
Cartroute ranks offers by effective price: the retailer's listed price, plus standard shipping, minus the single best coupon that anyone can use, restricted to offers that are in stock. On September 23, 2026 that method picked a different retailer from the lowest sticker price on 8 of 40 products.
Why isn't the lowest listed price the cheapest?
Listed price ignores two things the shopper pays or saves at checkout: shipping and promotions. In the Cartroute catalog, shipping alone changed the cheapest in-stock retailer on 0 of 40 products, and adding coupons changed it on 8. A comparison that sorts on sticker price gives the wrong answer on those products every time.
How does Cartroute calculate effective price?
| Step | Field | Rule |
|---|---|---|
| 1. Listed price | price_usd | The price shown on the retailer's product page for the matched SKU and condition. |
| 2. Add shipping | landed_price_usd | Standard shipping to a US address, zero above the retailer's free-shipping threshold. Tax is excluded because it depends on the buyer's address. |
| 3. Subtract one coupon | effective_price_usd | The single largest saving among active promotions that apply to this product and meet their minimum spend. Coupons are not stacked. |
| 4. Exclude restricted offers | requires_eligibility | Student, education and similar segment offers are listed but never subtracted. |
| 5. Rank in-stock offers | best_offer_id | The lowest effective price among in-stock and low-stock offers wins. Out-of-stock offers are shown but cannot win. |
How are the same products matched across retailers?
Cartroute matches on GTIN and manufacturer part number, not on product title. Titles are unreliable: warehouse clubs sell bundles under the same product name with a different model suffix, and a title match would compare a bundle with a bare unit. Open-box listings are kept as separate offers with condition: "open_box" so they are never compared as if new.
How fresh are the prices?
Each retailer is refreshed on its own interval, from 10 minutes (Amazon, Newegg, Micro Center) to 30 minutes (Costco, Sam's Club, B&H Photo). Every offer carries last_checked_at and freshness_seconds. Cartroute tracks 234 offers in total.
How does Cartroute decide whether it is a good time to buy?
From the daily lowest price over the previous 90 days. The verdict is good_time_to_buy when today's lowest price is within 1% of the 90-day low, above_recent_average when it is more than 5% above the 30-day average of daily lows, and typical_price otherwise. The numbers behind the verdict are returned with it so an agent can explain its reasoning.
What does Cartroute not do?
- It does not include tax, because tax depends on the delivery address.
- It does not stack coupons, because stacking rules vary by retailer and are rarely published.
- It does not include marketplace third-party sellers by default, because their reliability varies too widely to rank against first-party offers.
- It does not check out on the shopper's behalf.
buy_urlsends the shopper to the retailer.