Why your kundli doesn't match the one another site gave you
It's the single most common message an astrologer gets: “I cast my chart on two different sites and got two different answers — which one is right?” Usually, both are. Vedic astrology isn't one fixed algorithm; it's a tradition with a few genuine forks in the road, and most “mismatches” come from one of three places.
1. Which ayanamsa was used
Western astrology measures the zodiac from the moving equinox (tropical). Vedic astrology measures it against the fixed stars (sidereal) — and to convert one to the other you need a correction called the ayanamsa, currently a little over 24°. The catch is that there isn't one single agreed value. Lahiri (the Indian government's official standard, and what this site uses) is the most common, but KP (Krishnamurti) astrologers use a slightly different one, and a few traditions use others still. A degree or two of ayanamsa difference is enough to shift a planet sitting near the edge of a sign into the next sign entirely — which then cascades into a different house, a different dasha lord, sometimes even a different lagna. Neither number is “wrong”; they're answering slightly different questions.
2. Which house system was used
Even once the planets are placed, there's a second fork: how a chart splits the sky into twelve houses. The simplest method — whole sign — makes the entire sign your lagna falls in the 1st house, the next sign the 2nd, and so on. It's the classical default and what most Parashari readings are built on. A more precise method, Bhava Chalit (Sripati houses), instead measures the exact degree of the ascendant and midheaven and trisects the space between them — which means a planet sitting near the start or end of a sign can genuinely fall into a different house than the whole-sign method places it in. On this site's kundli report we show both readings side by side for exactly this reason: it's usually the real explanation when a planet “jumps house” between two calculators, not a bug in either one.
3. The birth time itself
This is the one worth actually checking before assuming the software is at fault. The lagna moves roughly one degree every four minutes, so a birth certificate that's off by even ten or fifteen minutes — not unusual with hospital clocks — can shift the ascendant enough to change the entire house framework of the chart, even though every planet's longitude is calculated identically. If two charts disagree sharply and the ayanamsa and house system match, the birth time is the first thing to re-check, ideally against the original hospital record rather than a family member's memory.
What to actually do with this
A small mismatch — a planet a house away, a dasha date off by a few weeks — is almost always ayanamsa or house-system convention, not error. A large one — a different lagna sign entirely, planets in wildly different signs — points to the birth time or the birth place coordinates. Either way, the fix isn't to distrust the calculation; it's to know which convention you're reading and hold the birth details fixed. Our own kundli maker states its ayanamsa (Lahiri) and shows both house systems openly, so you can see exactly which fork it took rather than getting a single unexplained answer.