BED Calculator
Calculate biologically effective dose, equivalent dose, and dose per fraction based on prescribed dose, fraction count, and alpha-beta ratio. BED Calculator supports radiotherapy planning and helps radiation oncologists, physicists, and clinicians compare fractionation schedules.
Highlights
- Estimate biologically effective dose (BED) for fractionated radiotherapy.
- Calculate dose per fraction from total dose and treatment fractions.
- Compare treatment schedules using equivalent dose in 2 Gy fractions.
- Customize calculations with tissue-specific alpha-beta ratios.
- Supports Gy and cGy units for flexible radiotherapy planning.
Table of Contents
How BED Calculator Works?
The BED Calculator uses the linear-quadratic model to estimate the biological effect of a fractionated radiotherapy schedule. Enter the total prescribed dose D, the number of fractions n, and the tissue-specific alpha-beta ratio α/β. The average dose per fraction is calculated first.
Here, d represents the dose delivered in each fraction. The biologically effective dose accounts for both the total physical dose and the effect of fraction size:
A lower alpha-beta ratio makes the calculation more sensitive to changes in dose per fraction, while a higher ratio indicates less sensitivity to fraction size. The equivalent dose in 2 Gy fractions is derived from the BED by setting the reference fraction size to 2 Gy:
For example, a schedule of 60 Gy in 30 fractions with an alpha-beta ratio of 10 Gy gives a dose per fraction of 2 Gy, a BED of 72 Gy, and an equivalent dose in 2 Gy fractions of 60 Gy.
| Quantity | Formula | Purpose |
|---|---|---|
| Dose per fraction | d = D / n | Average physical dose delivered in each fraction |
| Biologically effective dose | BED = D(1 + d / (α/β)) | Estimates biological effect for the selected tissue response |
| Equivalent dose in 2 Gy fractions | EQD2 = BED / (1 + 2 / (α/β)) | Provides a common reference for comparing fractionation schedules |
Practical Use Cases
Radiation oncologists: Compare conventional, hypofractionated, and other fractionation schedules while considering the assumed tissue-specific alpha-beta ratio. The BED and equivalent 2 Gy fraction outputs can support treatment-plan discussions and clinical evaluation.
Medical physicists: Review the physical dose per fraction and radiobiological estimates when checking fractionation plans, documenting dose schedules, or comparing alternative treatment prescriptions.
Radiotherapy clinicians: Use the calculator to communicate how total dose and fraction size influence estimated biological effect during multidisciplinary treatment planning and patient-care discussions.
Radiobiology researchers and students: Explore how changing the number of fractions or alpha-beta ratio changes BED and equivalent dose, helping illustrate the principles of the linear-quadratic model.
Accuracy and Limitations
The calculator performs the stated BED and equivalent-dose equations accurately from the entered total dose, integer fraction count, and alpha-beta ratio, subject to displayed rounding. Its results are model-based estimates: they assume the linear-quadratic model, uniform dose delivery, comparable biological conditions across fractions, and complete or clinically appropriate repair between fractions. They do not account for overall treatment time, repopulation, accelerated repair, dose-rate effects, treatment interruptions, spatial dose distribution, tumor heterogeneity, or patient-specific biology. The selected alpha-beta ratio strongly affects the result, and the output should support—not replace—professional radiotherapy planning and clinical judgment.
Quick Examples
Example #1: Conventional Prostate Treatment
Estimate the biological effectiveness of a conventional radiotherapy schedule for prostate cancer.
Example #2: Breast Hypofractionation
Evaluate the biologically effective dose for a moderately hypofractionated breast radiotherapy schedule.
Example #3: Stereotactic Body Radiotherapy
Compare the biological impact of a high-dose stereotactic treatment delivered in a small number of fractions.
