Calc Den is a free, unofficial fan site with calculators and data tables for Roblox games, headed 'Free Roblox calculators for what players really ask'. For Steal an Egg it has income and speed calculators, a treadmill and trail guide, a mutations guide, a 'what should I steal' tool, upgrade payback, a 265-pet list and an all-eggs list. It also has a Dandy's World research and unlock planner with a Toon list, and links to MapleStory Classic and Jam Bus Sandfall tools.
Each tool shows its formula and sources, and pet data is credited to the Steal an Egg Wiki (CC BY-SA 3.0). The site is available in English, Espanol, Portugues, Bahasa Indonesia, Tieng Viet, Deutsch and Francais. It is a website with no apps, and carries a notice that it is not affiliated with or endorsed by Roblox Corporation or the game's developers.
Calc Den gives Steal an Egg players quick answers to 'how much is this worth?', with each tool showing its formula and where the numbers come from.