Letrozole & Clomid Ovulation Calculator: Days 3–7 & 5

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Cycle day 1 (first day of period)

Medicine & dose

Pill schedule (5 days)

hCG trigger shot date (optional)Leave empty if no trigger was given.

Calculator Days 3–7 vs 5–9 chart Letrozole vs Clomid FAQ

Days 2–6 vs. 3–7 vs. 5–9: Letrozole & Clomid Ovulation Chart

Ovulation usually occurs 5–10 days after the last pill, most often about 7 days after. Starting later shifts every milestone later.

Pill days	Last pill	Start LH tests	Follicle scan	Expected ovulation	Pregnancy test
Days 2–6	Day 6	Day 9	Day 9–11	Day 11–16 (most often Day 13)	Day 20
Days 3–7	Day 7	Day 10	Day 10–12	Day 12–17 (most often Day 14)	Day 21
Days 4–8	Day 8	Day 11	Day 11–13	Day 13–18 (most often Day 15)	Day 22
Days 5–9	Day 9	Day 12	Day 12–14	Day 14–19 (most often Day 16)	Day 23

Days 3–7 is the most common schedule. Some clinics use an “extended” 10-day letrozole protocol or step-up dosing (2.5 → 5 → 7.5 mg) if you did not ovulate on the previous dose.

Letrozole vs. Clomid: Success Rates & Differences (ASRM / NEJM)

Feature	Letrozole (Femara)	Clomiphene (Clomid)
How it works	Aromatase inhibitor — lowers estrogen briefly so the brain releases more FSH	Blocks estrogen receptors in the brain, raising FSH
Half-life	≈2 days	≈5–7 days (metabolites last weeks)
Live birth in PCOS (PPCOS II, NEJM 2014)	27.5%	19.1%
Twin rate (PPCOS II)	≈3.4%	≈7.4%
Effect on uterine lining	Usually none	Can thin it in some women
Guideline position	First-line for PCOS anovulation	Alternative / unexplained infertility
Common side effects	Fatigue, dizziness, hot flashes	Hot flashes, mood changes, visual disturbance (stop & call doctor)

When should you have sex on letrozole or Clomid?

Start every-other-day intercourse 3 days after the last pill and continue until 2 days after a positive LH test.
If you had a trigger shot, have intercourse (or IUI) on the day of the trigger and 24–36 hours later.
Book a 7 DPO progesterone test to confirm the medicine worked before increasing the dose.
Seek care for severe abdominal bloating, pain or rapid weight gain (possible ovarian hyperstimulation).

Frequently Asked Questions

How many days after the last letrozole pill do you ovulate?

Most women ovulate 5–10 days after the last letrozole pill, most often around day 7 after it. On a Days 3–7 schedule that is typically cycle day 12–17.

Is letrozole better than Clomid?

For women with PCOS, yes: the NEJM PPCOS II trial found a 27.5% live-birth rate with letrozole versus 19.1% with Clomid, with fewer twins. International PCOS guidelines now recommend letrozole first-line. For unexplained infertility results are similar.

When should I start ovulation tests on Clomid or letrozole?

Start LH tests about 3 days after your last pill (cycle day 10 on a Days 3–7 schedule) and test twice daily, because the medicines can make the LH surge short.

Does letrozole cause twins?

It can, but less often than Clomid: about 3–4% twins versus 7–8%. Ultrasound monitoring helps your doctor cancel or adjust a cycle with too many mature follicles.

What if I don’t ovulate on letrozole?

Your doctor may increase the dose (2.5 → 5 → 7.5 mg), extend the course, add a trigger shot, or move to injectable gonadotropins. Confirm ovulation with a 7 DPO progesterone test or ultrasound.

⚠️ Official Medical Disclaimer

This calculator is for informational and educational purposes only. It produces mathematical estimates based on published clinical literature (ACOG, ASRM, ESHRE, NICE, WHO, NEJM) and is not a medical diagnosis, treatment plan, or method of contraception.

Every body and every treatment cycle is different. Always discuss your results with a qualified OB-GYN, reproductive endocrinologist, or fertility specialist before making any medical decision. Seek urgent care for heavy bleeding, severe one-sided pain, fainting, or fever.

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