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Fertilisation rate calculator

How many of my eggs fertilised?

Q: Why only count mature eggs?

Because immature eggs cannot fertilise. Dividing by total eggs retrieved rather than mature eggs understates the rate and makes cycles look worse than they were.

Q: What does a very low rate mean?

It points at the egg, the sperm, or the method. Total fertilisation failure after conventional IVF frequently leads to ICSI next time; failure after ICSI is rarer and prompts a different set of questions.

Q: Does a good fertilisation rate predict a good outcome?

It is a positive signal but a weak predictor on its own. The more informative number comes later — how many of those fertilised embryos reach blastocyst, which correlates far more closely with what happens at transfer.

The proportion of mature eggs that fertilised normally. One of the first real signals about egg and sperm quality that a cycle produces.

Normally fertilised (2PN)

Two pronuclei seen

Mature eggs (MII)

Total mature at retrieval

These are example numbers. Replace them with yours, then press Calculate.

Example answer

70%

65%+

A typical to good fertilisation rate. Around 70 to 80 percent is commonly quoted for ICSI and somewhat lower for conventional IVF.

This is a guide, not a diagnosis. Share the result with your doctor.

Your result on the scale

The ranges this calculator uses. Yours is highlighted.

Your numbers

Everything worked out from what you entered.

Normally fertilised: 7
Mature eggs: 10
Did not fertilise: 3

What each result means

Your result is highlighted. Your own clinic's advice always comes first.

Your result<25%

Low fertilisation. Where conventional IVF was used, ICSI is often considered next. Total or near-total failure has a specific set of causes worth investigating rather than repeating.

Your result25–50%

Below what most laboratories expect. Worth discussing whether the insemination method, sperm preparation, or egg maturity explains it.

Your result50–65%

Within the range many units report, though at the lower end. Often unremarkable in the context of a cycle that otherwise went well.

Your result65%+

A typical to good fertilisation rate. Around 70 to 80 percent is commonly quoted for ICSI and somewhat lower for conventional IVF.

Where this fits in your journey

The usual order, from trying to conceive to pregnancy. Not everyone needs every stage. This calculator belongs to stage 4.

Stage 4 · you are here

During an IVF cycle

Make sense of the numbers your clinic gives you.

Medicines
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Egg collection
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Your embryos

This calculator: How many of my eggs fertilised?

Calculators for what comes next

How this is worked out

Exact calculationArithmetic on the numbers you enter. If your inputs are right, this figure is right.

Fertilisation rate is normally fertilised 2PN embryos divided by mature eggs. Around 70 to 80% is commonly quoted for ICSI and somewhat lower for conventional IVF. Immature eggs are excluded because they cannot fertilise.

About this calculator

?What it tells you

Fertilisation rate. The proportion of mature eggs that fertilised normally. One of the first real signals about egg and sperm quality that a cycle produces.

✓When to use it

The morning after retrieval, when fertilisation numbers arrive

iWhat you need

Normally fertilised (2PN)
Mature eggs (MII)

!What it cannot tell you

Laboratory rates vary. These bands are general and your unit’s own figures are the right comparison.

Common questions

Why only count mature eggs?

Because immature eggs cannot fertilise. Dividing by total eggs retrieved rather than mature eggs understates the rate and makes cycles look worse than they were.

What does a very low rate mean?

It points at the egg, the sperm, or the method. Total fertilisation failure after conventional IVF frequently leads to ICSI next time; failure after ICSI is rarer and prompts a different set of questions.

Does a good fertilisation rate predict a good outcome?

It is a positive signal but a weak predictor on its own. The more informative number comes later — how many of those fertilised embryos reach blastocyst, which correlates far more closely with what happens at transfer.

Sources

Reference ranges vary by laboratory and by insemination method. Ask your unit for its own figures — good laboratories publish them.

In an emergency

If you have any of the warning signs listed here, don't wait for a test result or a calculator. Get help now.

112All emergencies, anywhere in India 108Ambulance

Also call your IVF clinic. Most clinics give an emergency number on your treatment or discharge sheet. Save it in your phone now, before you need it.