You are Manglik when Mars occupies the 1st, 2nd, 4th, 7th, 8th or 12th house counted from your ascendant, from your Moon, or from Venus - with the 1st house dropped from the Venus reckoning, because Mars sitting with Venus is treated as an antidote rather than an affliction. This calculator checks all three references, grades the severity, and lists the classical exceptions and cancellations that apply to your chart.
The affliction is a house position, so the first thing to fix is what the houses are counted from. AstroZivi checks Mars against three reference points: the Lagna, the Moon and Venus. From the Lagna and the Moon the Manglik houses are the 1st, 2nd, 4th, 7th, 8th and 12th. From Venus the same set applies minus the 1st.
That single omission is deliberate and it is the South Indian convention. Venus is the kalatra karaka, the significator of the spouse, and Mars conjunct Venus is read as the Bhrigu-Mangala combination rather than as a Venus-reference dosha. Counting the 1st from Venus would turn that conjunction into an affliction, which inverts the reading, so the house is dropped.
Two different mechanisms reduce a Manglik verdict, and this tool keeps them apart. An exception nullifies the dosha outright for that reference: the classical per-house table lists, for each Manglik house, the signs in which Mars produces no dosha at all - typically Mars's own, exalted or debilitated sign, or a natural benefic's sign for that bhava. A cancellation or mitigation instead reduces the severity without erasing the placement.
The severity grade you see, from None through Low and Mild to High, is set by that specific apparatus: the per-house exception signs, Mars associated with Mercury or the Moon, and Mars as a yogakaraka. The general parihara canon that AstroZivi applies across all doshas is also reported on the page, but deliberately does not reduce the Mangal grade a second time, because that would count the same relief twice.
Manglik dosha is traditionally examined before marriage, and the comparison is between charts rather than within one. The rule most often applied is that a Manglik and a Manglik are matched to each other, which is why the tool reports a plain Manglik status as well as an effective one with the classical exceptions already removed - the effective status is the one a matching verdict should use.
This page checks one chart. It tells you which reference the dosha comes from, in which house and sign Mars sits, which exceptions fired, and what the resulting grade is. A verdict about a pairing needs both charts, and that belongs to the Kundli matching tool, where the Manglik comparison sits alongside the Ashtakoota score and the other doshas.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.