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Although this project is free for everyone, hosting and domain costs have increased significantly. If you appreciate this project, consider contributing.
In living systems, biological processes fluctuate over time due to the integration of internal and environmental factors. Among these, circadian (~24-hour) oscillations are particularly significant and widely studied in physiology. To analyze 24-hour patterns in time-series physiological data, the cosinor model is commonly used. However, many existing native applications for cosinor analysis are outdated, irregularly maintained, and often incompatible with modern operating systems.
In addition to circadian rhythms, organisms also exhibit ultradian rhythms – shorter cyclic variations with periods less than 24 hours (e.g., 4–6 h or 90-minute cycles). These rhythms are particularly relevant in sleep physiology, hormonal regulation, and autonomic nervous system dynamics. Recognizing and quantifying such rhythms can provide deeper insights into physiological variability and system-level regulation beyond the 24-hour scale.
Cosinor.Online is a free, browser-based tool for analysing time-distributed biological data using the classic cosinor method. Designed as an enthusiast-driven project, it runs in modern web browsers and is hosted on secure remote servers — no installation required, with 24/7 availability.
Analyze 24-hour rhythmic data using a classic cosinor model:
Y = M + A × cos(2π × (t – φ) / T)
For detailed calculation formulas and implementation, see the manual of Cosinor calculations.
This tool is designed for physiological time-series data — such as hormone levels, activity, blood pressure, or temperature. The cosinor model helps quantify key rhythmic parameters: MESOR, amplitude, and acrophase.
In addition to circadian rhythms (~24 h), the app supports ultradian cycles (shorter than 24 h), such as 90-minute sleep cycles or 4-hour feeding rhythms.
The project is maintained by Lubos Molcan, Ph.D. and runs on a secure, high-availability server with 24/7 access. If you use this tool in your research, please cite the following publication:
Although this project is free for everyone, hosting and domain costs have increased significantly. If you appreciate this project, consider contributing.