Peer Richelsen
Peer Richelsen is a German-born entrepreneur who co-founded the scheduling company Cal.comCal.comCal.com is a scheduling software company founded in 2021 by Peer Richelsen and Bailey Pumfleet as Calendso, an open-source alternative to Calendly, and renamed Cal.com later that year. It raised a $7.4 million seed round led by OSS Capital in 2022, and its backers also include Seven Seven Six; in April 2026 it announced it was moving from open source to closed source, citing AI-driven security risks, while keeping an open version as Cal.diy.Open the full entry (originally Calendso) with Bailey PumfleetBailey PumfleetBailey Pumfleet is a British developer and entrepreneur who co-founded Cal.com and is its chief executive. He joined Peer Richelsen within weeks of the first Calendso commit and built much of the early product; in April 2026 he announced that Cal.com was moving from open source to closed source.Open the full entry in 2021 and leads its product and engineering. He previously founded Mage Market, a Magic: The Gathering card marketplace that was accepted into Y Combinator in 2019 and shut down during the pandemic in 2020.
Contents4 sections
Key facts
2017–2020Mage Market
Richelsen grew up on a small farm in Germany, where his father was a farmer. His first business was bordifies.com, a protective sleeve for Magic: The Gathering cards that went viral on RedditRedditReddit is an online platform that organizes content and discussion around interest-based communities, founded by Steve Huffman and Alexis Ohanian in 2005. Users take part in communities by posting, commenting, and voting; its operating company, Reddit, Inc., listed on the New York Stock Exchange in 2024.Open the full entry and sold globally. In 2017 he started Mage Market, a peer-to-peer marketplace for the cards, which was accepted into Y Combinator in 2019 and shut down during the pandemic in 2020; he also ran a bootstrapped company, Leanhire.com, that was sold within the same year.[1]
From 2021Cal.com
In 2021 he co-founded Cal.com with Bailey Pumfleet as Calendso, because every scheduling tool at the time was closed and none could be embedded. He leads product and engineering at Cal.com and builds in public on X (@peer_rich). He has said the two most important milestones for him and Bailey were the Product HuntProduct HuntProduct Hunt is a product-discovery and launch community founded by Ryan Hoover in 2013 and operated by Product Hunt, Inc. Makers present new products, while users vote, comment and review them and discover tools through categories, forums and AI search. AngelList announced its acquisition in 2016; as of November 2026, its official website lists Rajiv Ayyangar as CEO.Open the full entry launch, which became Product of the Month, and the rebrand to Cal.com soon after.[2][1]
Cal.com raised a $7.4 million seed round led by OSS Capital in 2022; he signed the announcement.[3]
Related Organizations, Websites, and Public Accounts
Cal.com: Official website: https://cal.com/ (opens in a new window).[2]
LinkedInLinkedInLinkedIn is a social networking platform for professionals. It was founded in 2002 by Reid Hoffman and others, launched in 2003, and listed on the New York Stock Exchange in 2011; after Microsoft acquired it for approximately $26.2 billion in 2016, it became a wholly owned Microsoft subsidiary. Its revenue comes from membership subscriptions, advertising, and recruitment solutions.Open the full entry: https://www.linkedin.com/in/peer-richelsen-221233138/ (opens in a new window).[2]