Calculation research
How Fast Does the Rising Sign Change? Latitude & Sign Speed Table
By Natal Chart Lab ·
The rising sign changes about every two hours on average, but individual signs do not take equal time to rise. At 45° north, this reference calculation gives Aries 64.6 minutes and Leo 158.5 minutes. Latitude and the part of the zodiac on the eastern horizon matter.
Use the rising sign calculator for your actual birth time and place. The table below describes full sign durations; it cannot tell you how close your birth was to the next sign boundary.
Minutes per rising sign, by latitude
| Sign | 60° S | 45° S | 30° S | 0° | 30° N | 45° N | 60° N |
|---|---|---|---|---|---|---|---|
| Aries | 193.4 | 158.0 | 138.2 | 111.3 | 84.5 | 64.6 | 29.3 |
| Taurus | 194.6 | 158.5 | 141.3 | 119.3 | 97.4 | 80.1 | 44.0 |
| Gemini | 165.1 | 145.0 | 137.4 | 128.4 | 119.3 | 111.8 | 91.6 |
| Cancer | 91.6 | 111.8 | 119.3 | 128.4 | 137.4 | 145.0 | 165.1 |
| Leo | 44.0 | 80.1 | 97.4 | 119.3 | 141.3 | 158.5 | 194.6 |
| Virgo | 29.3 | 64.6 | 84.5 | 111.3 | 138.2 | 158.0 | 193.4 |
| Libra | 29.3 | 64.6 | 84.5 | 111.3 | 138.2 | 158.0 | 193.4 |
| Scorpio | 44.0 | 80.1 | 97.4 | 119.3 | 141.3 | 158.5 | 194.6 |
| Sagittarius | 91.6 | 111.8 | 119.3 | 128.4 | 137.4 | 145.0 | 165.1 |
| Capricorn | 165.1 | 145.0 | 137.4 | 128.4 | 119.3 | 111.8 | 91.6 |
| Aquarius | 194.6 | 158.5 | 141.3 | 119.3 | 97.4 | 80.1 | 44.0 |
| Pisces | 193.4 | 158.0 | 138.2 | 111.3 | 84.5 | 64.6 | 29.3 |
Why “two hours” is an average
Earth turns relative to the stars in about 23 hours 56 minutes. The unrounded durations in each table column sum to 1436.068 minutes, rather than 1,440. Dividing by 12 gives about 119.7 minutes per sign. Even at the equator, equal ecliptic arcs do not correspond to equal right-ascension arcs, so the durations differ.
In northern latitudes some signs have long ascension and others short ascension. The pattern reverses across the equator: compare the northern and southern columns rather than applying a northern-hemisphere rule everywhere. Longitude sets when the sequence occurs on the local clock; it does not change these full-sign durations at a fixed latitude and obliquity.
How this table is calculated
For each 30° zodiac boundary, convert ecliptic longitude to right ascension α and declination δ. At geographic latitude φ, the rising hour angle is −acos(−tan φ tan δ), so local sidereal angle at rising is α − acos(−tan φ tan δ). Take the forward difference between successive boundaries and convert a 360° rotation to 86164.0905 seconds.
The reference obliquity is 23.437676° at 2000-01-01 12:00 UTC. It is held constant for the table, which is a reference model, not a date-specific ephemeris. Values are rounded to 0.1 minute; that display precision is not an accuracy guarantee. The table excludes latitudes beyond ±60°, where polar horizon geometry needs separate treatment; do not extrapolate it to all latitudes. Atmospheric refraction and terrain are not included in the astrological Ascendant.
Download the research JSON · Reproduce these tables (TypeScript source). Research output is CC BY 4.0; attribute Natal Chart Lab and link to this article.
Does a 15-minute time error change my rising sign?
It can if the recorded time lies near an ingress. A sign lasting 150 minutes can still change within one minute of a particular birth time. Read our calculated birth-time comparison, then check the time range with your birthplace in the calculator. A duration table cannot recover a missing birth time.
Prepared with AI assistance and checked against calculation code and saved data. Tables state their definitions and limits; astrological interpretations are not established by these calculations.