In case you haven’t already been accosted by your friendly neighborhood mathlete, it’s Pi day today. Microsoft is celebrating the semi-momentous day with its usual Pi Day sale, which takes 31.4% (yes, we see what you did there) off Windows Mixed Reality headsets, along with a bunch of laptops from Dell, Alienware, HP, and Lenovo.

The sale is only applied on the Microsoft Store, where products are normally listed at full price. You can find some of these laptops for a little less than the stated RRP elsewhere, making this deal a little less appealing, but the savings on some of the newer models are still substantial.

Some of the best deals are the Dell XPS 13 for $1,099, normally $1,399; the XPS 15 for $1,299, normally $1,649; and the Alienware 15 R3 gaming laptop, which is $1,474, down from $2,149. Even bigger savings apply if you buy the more expensive, higher-specification versions of those machines.

There are also some laptops on sale for $314 to mark Pi Day. Models include the Asus Vivobook Flip 12, the Dell Inspiron 13, and the Lenovo Ideapad Flex 5. Those are all slightly older models with older-generation Intel CPUs compared to what you’d find in the same PCs today. Nonetheless, for $314, the specs on the Lenovo laptop in particular (Intel Core i5, 8GB RAM, 1080p screen) are way better than what you’ll find on any other $300 Windows PC.