EQD2 Calculator
Convert fractionated radiation doses to standard 2 Gy equivalents using the linear-quadratic model. Trusted by radiation oncologists, medical physicists, and dosimetrists for hypo-fractionation comparison & treatment plan normalization.
where D = total dose (Gy), d = dose per fraction (Gy), α/β = tissue-specific ratio.
Interactive EQD2 Calculator
Enter total dose, dose per fraction, and alpha/beta ratio (commonly 10 for tumors, 3 for late-responding tissues). Get instant EQD2 (equivalent dose in 2 Gy fractions).
📊 Equivalent Dose in 2 Gy fractions (EQD2)
Alpha/Beta Ratio Reference Table (2026)
| Tissue / Tumor Type | Typical α/β ratio (Gy) | Clinical Note |
|---|---|---|
| Early-responding tissues / most tumors | 10 | Standard for squamous cell, many solid tumors |
| Late-responding tissues (spinal cord, kidney, lung) | 2–3 | High sensitivity to fraction size |
| Prostate adenocarcinoma | 1.5 – 3 | Low α/β → hypofractionation beneficial |
| Breast cancer (early) | 4 | Moderate, used in hypo-fractionated regimens |
| Skin / mucosa (acute reactions) | 10 | Standard for acute effects |
| Optic nerve / brainstem | 2–2.5 | Very sensitive to fraction size |
Pro Insight (2026): The American Brachytherapy Society recommends EQD2 for comparing HDR and LDR brachytherapy schedules. Use our calculator for prostate, cervix, and breast boost planning.
EQD2 Calculation Examples & BED Relationship
🔢 Example 1: Conventional fractionation
Total dose 60 Gy, 2 Gy/fraction, α/β = 10 → EQD2 = 60 × (2+10)/(2+10) = 60 × (12/12) = 60 Gy. No change (baseline).
⚡ Example 2: Hypofractionated (prostate SBRT)
36.25 Gy in 5 fractions (7.25 Gy/fraction), α/β = 1.5. EQD2 = 36.25 × (7.25+1.5)/(2+1.5) = 36.25 × (8.75/3.5) = 36.25 × 2.5 = 90.6 Gy (high biologically effective dose).
📘 BED (Biologically Effective Dose) conversion
BED = D × (1 + d/(α/β)). Our EQD2 directly links to BED via: EQD2 = BED / (1 + 2/(α/β)). Use the EQD2 calculator to cross-check hypofractionated regimens against conventional schedules. This is the bed and eqd2 calculator synergy: both quantify biological effect.
EQD2 Calculation Checklist (2026 Clinical Best Practices)
- ✔️ Verify α/β value from recent literature (ASTRO/ABS guidelines).
- ✔️ For brachytherapy EQD2 calculator, use prescribed dose to 90% isodose line (EQD290).
- ✔️ When comparing multiple phases (EBRT + boost), sum EQD2 contributions.
- ✔️ Always re-calculate if fractionation changes mid-treatment.
- ✔️ For spinal cord constraints: keep EQD2 (α/β=2) below 50 Gy (conventional).
How to Calculate EQD2: 4 Simple Steps
- Identify total dose (Gy) — sum of all fractions delivered.
- Determine dose per fraction — typical 1.8–2.0 Gy or hypo-fractionated.
- Select appropriate α/β ratio — using table above (tumor or OAR).
- Apply formula: EQD2 = D × (d + α/β) / (2 + α/β).
Or simply use our dynamic eqd2 dose calculator above — real-time results with no manual math.
Frequently Asked Questions (EQD2)
EQD2 (Equivalent Dose in 2 Gy fractions) converts any fractionation schedule into the biologically equivalent total dose delivered at 2 Gy per fraction, using the linear-quadratic model with alpha/beta ratio.
ABS recommends the same LQ formula. Our calculator includes alpha/beta presets for prostate, cervix, and HDR brachytherapy — providing ABS-compliant EQD2 values for clinical reporting.
BED (Biologically Effective Dose) is a raw value, while EQD2 normalizes to 2 Gy/fraction for easier comparison. Both are derived from α/β. Our page provides bed calculator eqd2 relationship.
Yes, with Relative Biological Effectiveness (RBE) adjustments. For most clinical proton plans, RBE of 1.1 is used, then EQD2 conversion applies similarly.
TotalCalcHub’s eqd2 calculator app is web-based and free. No downloads required — works on mobile, desktop, and tablets. Use it for research or daily clinical workflow.
For HDR, enter total prescribed dose (e.g., 21 Gy in 3 fractions of 7 Gy), select alpha/beta for target (e.g., 10), and the calculator yields EQD2. Example: 21 × (7+10)/(2+10) = 29.75 Gy EQD2.
The standard linear-quadratic formula is globally adopted. The kathmandu eqd2 calculator or mdcalc version uses the same principle. Our tool is consistent with worldwide clinical physics standards.
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Clinical & Legal Disclaimer
This EQD2 calculator is an educational tool intended for medical physicists, radiation oncologists, and students. Always verify results with institutional protocols and a qualified professional. The American Brachytherapy Society recommends using validated software. TotalCalcHub provides estimates only; not a substitute for clinical judgment. By using this calculator you agree to our Terms of Use. 2026 edition.