How this calculator works
The linear-quadratic model combines total physical dose, uniform fraction dose and tissue alpha/beta. For short fractions with full inter-fraction repair, G is 1. A supplied per-fraction repair factor can reduce the quadratic contribution for prolonged irradiation; this tool does not estimate G from treatment duration. The EQD2 reference assumes brief 2 Gy fractions. It does not model repopulation, incomplete repair between fractions, mixed fraction sizes or a tissue-specific alpha/beta choice. The result is an estimate for information only and is not medical advice.
Formula
For identical fractions with full repair between them: BED = D x [1 + G x d/(alpha/beta)]. EQD2 = BED/[1 + 2/(alpha/beta)]. D is total dose, d is dose per fraction and G is the known per-fraction repair factor. Inverse modes rearrange the BED equation.
Worked example
For 60 Gy in 2 Gy fractions, alpha/beta 10 Gy and G = 1, BED = 60 x 1.2 = 72 Gy and EQD2 = 72/1.2 = 60 Gy. For 30 Gy in 3 Gy fractions, BED is 39 Gy and EQD2 is 32.5 Gy.
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Frequently asked questions
Which alpha/beta should I enter?
Use a value justified for the tissue and endpoint being studied. The default is an arithmetic example, not a recommendation for any tumour or organ.
Does a longer fraction always use the same G?
No. G depends on dose delivery and repair kinetics. Enter an independently justified per-fraction value; this tool does not infer one from a broad duration category.
Can BED replace treatment planning?
No. The model has limits, particularly at unusual fraction sizes and schedules. Specialist treatment planning and clinical judgement remain necessary.