Freedom251 › Scientific Calculator Apps
Castiel
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| Linux | Free in full; no session timer. · Linux · every mode · Debian, Flatpak, AppImage, tarball | Free |
| Free tier | No time limit for Simple and School; advanced modes limited to about 30 minutes per session. · Simple and School · paper tape · advanced modes about 30 minutes/session | Free |
| Windows full version | One-time purchase; removes the session limit on advanced modes. · Windows · all modes · editable tape | $2, paid once |
As castiel.dmkilab.com lists them, read 14 Nov 2026. The maker's own page has the final word.
Facts from Castiel's own pages
- Accessibility
- The app supports keyboard operation and native desktop screen-reader systems for Windows, macOS, and Linux. · castiel.dmkilab.com, 14 Nov 2026
- AI providers
- Programming+ can use user-supplied Anthropic, OpenAI, Qwen, or DeepSeek providers; Castiel has no built-in AI. · castiel.dmkilab.com, 14 Nov 2026
- API key security
- AI provider keys are held in the operating system's secure store and are not shared with Castiel's authors. · castiel.dmkilab.com, 14 Nov 2026
- Calculator modes
- Castiel combines six calculator modes with a shared computation engine and editable paper tape. · castiel.dmkilab.com, 14 Nov 2026
- Connectors
- Optional connectors support live currency rates, custom web endpoints, AI providers, and receipt printers. · castiel.dmkilab.com, 14 Nov 2026
- Engineer features
- Engineer mode includes computer algebra, matrices, units, constants, numerical methods, and plotting. · castiel.dmkilab.com, 14 Nov 2026
- Financial tools
- Financial mode covers time value of money, cash flow, amortization, bonds, depreciation, breakeven, and interest conversion. · castiel.dmkilab.com, 14 Nov 2026
- Headquarters
- Dublin, Ireland · castiel.dmkilab.com, 19 Oct 2026
- Paper tape
- The editable paper tape is shared across modes and supports revising earlier calculations. · castiel.dmkilab.com, 14 Nov 2026
- Platform availability
- The opened download page lists Windows and Linux as available, Android in open testing, and macOS and iOS as coming soon. · castiel.dmkilab.com, 14 Nov 2026
- Privacy and data
- Calculations, saved tapes, and settings are stored locally, and connectors are optional; no outside connections occur if none are configured. · castiel.dmkilab.com, 14 Nov 2026
- School features
- School mode includes graphing, statistics, equations, spreadsheets, and other learning tools. · castiel.dmkilab.com, 14 Nov 2026
Where Castiel stands on Freedom251
- Scientific Calculator Apps#6 of 32