Egg Freezing Calculator — Oocytes Needed for Live Birth
Find the number of mature oocytes needed to reach a desired probability of at least one live birth, using age-adjusted per-egg success rates from published SART and HFEA data.
Age group at egg retrieval
%
%
Minimum mature eggs to reach the desired probability
- 1
Desired probability (decimal)
80 ÷ 100 = 0.8 - 2
Minimum eggs (continuous)
log(1 − 0.8) ÷ log(1 − 0.055) = 28.45Inversion of the binomial "at least one" formula P = 1 − (1 − r)^N. - 3
Mature oocytes to freeze (ceiling)
⌈28.45⌉ = 29
How does this calculator work?
Eggs to freeze: N = ⌈log(1 − p) / log(1 − r)⌉ where p is desired probability and r is per-egg live birth rate (≈ 5.5 % under 35, declining with age). Freezing 15–20 mature oocytes typically gives a 50–70 % cumulative probability of at least one live birth for women under 38.
Formula
How this is calculated
Each mature oocyte retrieved and vitrified (frozen) has an independent probability r of resulting in a live birth — accounting for freeze-thaw survival (≈ 80 %), fertilisation (≈ 70 %), blastocyst development (≈ 40 %), and implantation rates. The cumulative probability of at least one live birth from N eggs follows the binomial model: P(≥ 1 live birth) = 1 − (1 − r)^N. Inverting this gives the minimum number of eggs needed: N = ⌈ log(1 − p) / log(1 − r) ⌉.
Per-egg rates decline with age: approximately 5.5 % for women under 35, 4.0 % at 35–37, 2.5 % at 38–40, 1.5 % at 41–42, and 0.8 % over 42, based on clinic-reported outcomes from the SART national registry and UK HFEA data (figures represent 2022–2024 averages). These are population estimates — individual outcomes depend on ovarian reserve, embryo quality, uterine factors, and clinic protocols. If your clinic has published its own per-egg cumulative live birth rate, enter it in the custom field to override the age-group estimate.
Limitations: the model assumes independence between oocytes and a fixed per-egg rate regardless of how many cycles are needed to collect them. Actual results vary widely. This calculator is a planning tool only — it does not replace a consultation with a reproductive endocrinologist who can assess your individual ovarian reserve (AMH, AFC) and recommend a personalised number of collection cycles.
Frequently asked questions
At 35–37, with an estimated 4 % per-egg live birth rate, reaching an 80 % cumulative probability requires approximately 40 mature oocytes. For a 60 % target, about 22 eggs suffice. These are population averages — individual success rates depend on egg quality, clinic techniques, and the recipient's uterine environment.
Of total eggs retrieved during a cycle, typically 70–80 % are mature (MII-stage) and suitable for freezing. The per-egg rates in this calculator apply to mature oocytes only. If your clinic reports total retrieved eggs, multiply by 0.75 to estimate mature yield.
Modern vitrification achieves 80–90 % oocyte survival after thawing with minimal impact on fertilisation or embryo quality compared to fresh eggs. Studies show comparable live birth rates for vitrified donor eggs and increasingly similar outcomes for autologous vitrified oocytes from younger women.
Also known as
TG we-Calculate Editorial Team. (2026). Egg Freezing Calculator — Oocytes Needed for Live Birth [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/egg-freezing-calculator
TG we-Calculate Editorial Team. "Egg Freezing Calculator — Oocytes Needed for Live Birth." TG we-Calculate. 2026. https://we-calculate.com/calculator/egg-freezing-calculator.
TG we-Calculate Editorial Team, "Egg Freezing Calculator — Oocytes Needed for Live Birth," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/egg-freezing-calculator
@misc{wecalculate_egg_freezing_calculator, title = {Egg Freezing Calculator — Oocytes Needed for Live Birth}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/egg-freezing-calculator}}, year = {2026}, note = {TG we-Calculate} }
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