Calculate EQD2, BED, and fraction dose quickly. Switch between input modes easily. Keep planning consistent across treatments.
This calculator applies the linear-quadratic model. Let total dose be D, fractions be n, fraction dose be d = D/n, and α/β be the tissue ratio.
Illustrative comparisons using α/β = 3 Gy. Values are rounded for readability.
| Regimen | Total Dose (Gy) | Fractions | Dose/Fx (Gy) | BED (Gy) | EQD2 (Gy) |
|---|---|---|---|---|---|
| Conventional | 60 | 30 | 2.0 | 100 | 60 |
| Hypofractionated | 40 | 15 | 2.67 | 75.6 | 45.4 |
| Stereotactic | 30 | 5 | 6.0 | 90 | 54 |
EQD2 translates varied fractionation schemes into a common reference: the dose that would produce a similar biological effect if delivered in 2 Gy fractions. This helps compare protocols across sites, machines, and schedules when physical dose alone is misleading.
The model separates damage into linear and quadratic components. The α/β ratio controls how sensitive the tissue is to fraction size. Lower α/β increases the impact of larger fractions, raising EQD2 and BED for the same total dose.
Many planning discussions use α/β ≈ 3 Gy for late-responding effects and ≈ 10 Gy for early-responding effects. For an identical regimen, EQD2 differs markedly between these ratios, so documenting the chosen value is essential for audits and comparison.
BED summarizes biological intensity, while EQD2 expresses that intensity on a 2 Gy-per-fraction scale. For example, with α/β = 3 Gy, 30 Gy in 5 fractions gives BED = 90 Gy and EQD2 ≈ 54 Gy, highlighting the strong fraction-size effect.
Good inputs reduce interpretation errors. Confirm units (Gy), confirm that fractions are positive, and ensure the total dose matches dose-per-fraction times fractions when using that mode. Small entry mistakes can shift EQD2 enough to change conclusions.
When comparing regimens, keep α/β constant and report both EQD2 and BED. If 60 Gy/30 fractions yields EQD2 of 60 Gy at any α/β, a hypofractionated plan may show lower or higher EQD2 depending on α/β and fraction size.
CSV supports quick spreadsheet review and charting, while the PDF snapshot supports recordkeeping. Including mode, α/β, dose inputs, BED, and EQD2 on every export helps reproducibility and reduces “what assumptions were used?” follow-ups.
EQD2 is an approximation, not a guarantee of clinical equivalence. It does not automatically include time factors, repair kinetics beyond the basic model, or patient-specific biology. Use EQD2 as a structured comparison tool, alongside protocol guidance and professional judgment.
EQD2 is the dose, in 2 Gy fractions, expected to produce a similar biological effect as the entered regimen under the linear-quadratic model and the selected α/β ratio.
BED expresses biological intensity directly. EQD2 converts BED into an equivalent 2 Gy-per-fraction dose using the same α/β ratio, which can be easier to compare across plans.
Use the α/β appropriate for the tissue or endpoint being compared. Common defaults are 3 Gy for late effects and 10 Gy for early effects, but protocol-specific values may differ.
Fraction size appears in the model term (1 + d/(α/β)). Larger d increases BED and EQD2, especially when α/β is small, reflecting greater sensitivity to hypofractionation.
Yes. Select the BED mode and enter BED plus α/β. The calculator applies EQD2 = BED / (1 + 2/(α/β)) to produce the equivalent 2 Gy reference dose.
Displayed values are rounded for readability, but exports keep more decimals. If you need a specific precision standard, you can copy the CSV into a spreadsheet and format the output.
No. This version focuses on the core linear-quadratic conversion. If you need time corrections, you can extend the tool by adding overall treatment time and a repopulation term.
Use EQD2 carefully; document assumptions; share results responsibly.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.