Moon Sighting (Hilal) Calculator
Last updated: June 2026 · Free · No sign-up required
Enter values above and click Calculate to see your result instantly.
Every Islamic month turns on one question: can the new crescent be seen tonight? This calculator answers it astronomically — it finds your local sunset and moonset, measures the moon’s age since conjunction, its altitude, elongation and crescent width at the best observation time, and grades visibility with the Yallop q-criterion used by professional crescent observers, from zone A (easily visible) to F (impossible).
The positions come from Meeus solar and lunar algorithms validated to a few hundredths of a degree, and the verdict respects the Danjon limit — below 7° elongation no crescent can physically form. Use it to understand why Ramadan or Eid starts when it does in your country, or to plan an actual sighting attempt: it tells you exactly when to look and how long you have before the hilal sets.
Quick reference
| Yallop zone | q-value | Meaning |
|---|---|---|
| A | q > +0.216 | Easily visible to the naked eye |
| B | −0.014 < q ≤ +0.216 | Visible under perfect conditions |
| C | −0.160 < q ≤ −0.014 | May need optical aid to find first |
| D | −0.232 < q ≤ −0.160 | Binoculars or telescope only |
| E/F | q ≤ −0.232 | Not visible |
mosque Calculated to Shariah-compliant formulas
Every Islamic calculator on CalcaTools uses formulas from recognised Shariah authorities — the Hilal Committee's Hijri conversion tables, the MWL/ISNA/Umm al-Qura prayer-time methods, the four-school consensus for Zakat Nisab, and the Faraid distribution rules from classical fiqh. The exact authority is cited on every tool page.
menu_book Sunni & Shia rules side by side
For tools where the calculation differs between schools (Faraid inheritance, certain Zakat triggers, prayer-time conventions), we surface the choice as a selector and document the difference in the methodology block. Pick the school that matches your tradition — the answer adjusts.
savings Zakat with the live Nisab
Zakat tools fetch the current spot gold/silver price (or let you enter your local rate) so the Nisab threshold reflects today's value, not a stale figure from last year. The 2.5% rate is the standard hawl-based calculation; agricultural Zakat (1/10 or 1/20) is available on the dedicated Ushr calculator.
verified For guidance, not a fatwa
These calculators give you the number — they do not give a fatwa. For complex personal situations (inheritance with revoked rights, mixed-asset Zakat, late prayer makeup rules), please confirm with a qualified scholar in your tradition. We're here to help with the arithmetic, not to replace your local imam.
Interpretation guide
| Indicator | Rule of thumb |
|---|---|
| Moon age | 24h: usually sightable somewhere |
| Lag time | 50 min: promising |
| Elongation (ARCL) | < 7° (Danjon limit): physically impossible to see |
| Negative lag | Moon sets before the sun — impossible that evening |
Formula & methodology
Formula: q = (ARCV − (11.8371 − 6.3226W + 0.7319W² − 0.1018W³)) ÷ 10, at best time = sunset + 4⁄9 × lag
- Pick the evening and enter latitude, longitude and UTC offset.
- The calculator finds local sunset, then moonset, and evaluates the sky at the “best time” = sunset + 4⁄9 of the lag.
- Sun and moon positions come from Meeus algorithms (validated to <0.03°); moon age is measured from the true conjunction (new moon).
- The Yallop q-test combines crescent altitude (ARCV) and width (W) into zones A–F.
Worked example: Makkah on 18 Feb 2026 (eve of Ramadan 1447): conjunction was 17 Feb 3:02 PM, so the moon is 27.3 hours old at sunset (6:19 PM), sets 55 min later, elongation 14.2°, q = +0.43 → zone A: easily visible — matching the actual Ramadan start on 19 Feb.
Frequently asked questions
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