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. In live prices on November 8, 2026, that method picked a different retailer from the lowest sticker price on 7 of 36 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 Cartroute preview pricing, shipping alone changed the cheapest in-stock retailer on 7 of 36 products, and adding coupons changed it on 7. 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 groups listings from different stores when they share a model number and the same brand, or when their titles are nearly identical. Listings whose storage size or screen size differs are never grouped, bundles are kept apart from the bare product, and auctions and out-of-stock listings are dropped. Renewed, refurbished, open-box and used offers are kept but labelled, and never chosen as the best price while a new unit is in stock. Every offer keeps the retailer's own listing title, so the exact configuration can always be checked.
How fresh are the prices?
Searches are sent to the retailers when they arrive and the results are reused for a few hours; tracked products are re-checked every day. Every offer carries last_checked_at and freshness_seconds. Cartroute tracks 4,453 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.