Whenever you try to change quantity from the cart and that quantity is not available in the inventory, unit price is wrong.

Example: I add Product A in the cart (simple product), first time I choose a quantity 1 from product detail page.

After that, I decide to change cart quantity to 3 and press Update button in the cart. In my inventory there are only 2 stock units of Product A.

Magento throw correctly a notice that is not possible to add 3 stock units in the cart for Product A but if you see under the unit price column, its price has been changed.

With a quantity of 2, unit price is 41,50 Euro, with a quantity of 3 unit price become 18,59 Euro. If I change quantity to 4, unit price become 9,37 Euro. So every time quantity is changed, it seems that unit price has been recalculated for some reason.

Is there a logical explanation to this strange behaviour?

Magento installed version:

  • Can you please check in admin (manage product section) if there are any tier price entered for the product?
    – Twinkle
    Oct 24, 2017 at 9:49

1 Answer 1


This seems to be a bug introduced in Magento Not sure what reason for the change but this person's post was the same solution that I came to: https://community.magento.com/t5/Version-Upgrades/Cart-displays-wrong-price-after-exceeding-stock-value-Version-1/m-p/72784/highlight/true#M2453

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