Home / Calculators / Ovarian response / Follicular output rate (FORT)
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A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
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These tools provide general information and are not a diagnosis or a substitute for assessment by a qualified clinician. Reference ranges and sources are stated on each calculator. Predictive estimates describe groups of people and cannot predict an individual outcome.
A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
Free first consultation. No obligation to start treatment, and it doesn't affect your care at your current clinic.
How many of your antral follicles actually responded to stimulation.
Exact calculationArithmetic on the numbers you enter. If your inputs are right, this figure is right.
Follicular output rate is the number of pre-ovulatory follicles divided by the antral follicle count, showing how many available follicles actually responded to stimulation. A low FORT points at the protocol rather than at ovarian reserve.
Source — FORT was described by Genro et al. Cut-offs used in the literature vary; the low/intermediate/high tertile split is the most common presentation.
16–22mm on trigger day
At baseline scan
That falls in the 60%+ band.
Your result of 64 % sits in the highlighted band. Bands are reference points used alongside clinical findings — not a diagnosis.
Good follicular response — most of the available cohort responded to stimulation.
FORT was described by Genro et al. Cut-offs used in the literature vary; the low/intermediate/high tertile split is the most common presentation.
Highlighted is the stage this measurement belongs to. It is a map of the process, not a schedule — timings vary by protocol and by clinic.
Those measure how many follicles are available. FORT measures how many of them actually responded. Someone can have a reasonable AFC and a poor FORT, which points at the protocol rather than at reserve.
Sometimes. It is one of the findings that prompts a change of stimulation approach rather than a change in expectations, which makes it a useful thing to ask about after a disappointing cycle.
No, and the distinction matters. Reserve is how many follicles you have; FORT is how many of them responded. A normal antral count with a low FORT points at the stimulation protocol, which is adjustable — that is a much more hopeful finding than low reserve.
A calculator sees three or four figures. A specialist sees your history, your scans, your partner's results, and how you actually responded to treatment. If you're between cycles, changing clinics, or something in your results doesn't add up, a second opinion is the fastest way to find out whether anything would be done differently.
Free first consultation. No obligation to start treatment, and it doesn't affect your care at your current clinic.
FORT is a research-derived index used alongside clinical judgement, not a standalone measure. Nothing here is a diagnosis or a substitute for assessment by a clinician.
A calculator gives you a number. These explain what it means, and what it does not.
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