How to Find Your House Cusps: All Twelve, by Degree

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A house cusp is the exact zodiac degree where a house begins. Your natal chart has twelve of them, fixed for life by the moment and place of your birth. You need them as numbers whenever the question is "which house is this degree in?": a planet close to a house line in your own chart, a transiting planet moving through your houses, or another person's planet placed in your chart. This page is the full workflow, from the birth data you enter to the arithmetic that settles a borderline case.

What the free chart shows: the free birth chart draws the twelve cusp lines on the wheel, numbers the houses, and marks the ASC, DC, MC and IC. It does not print a table of cusp degrees, and it does not print the Ascendant's degree as a number. So the twelve values have to come from a calculation source that lists them. This page tells you exactly what to match and gives a complete worked table to compare against.

House cusps need a reliable birth time. Without one, the free chart withholds the Rising sign and the houses altogether, and no cusp source can honestly supply them either; a chart without a birth time explains what remains usable.

What a cusp longitude is

Every position in the zodiac can be written two ways: as a sign and a degree (21°46' Libra) or as a single longitude counted from 0° Aries, running from 0° up to just under 360°. To convert, add the start of the sign to the degree and turn the minutes into a decimal:

So 21°46' Libra is 180 + 21 + 46/60 = 201.77°. Longitudes make the house question a matter of subtraction instead of a judgement by eye.

Step 1: write down the birth data exactly

A cusp source calculates from four inputs, and a mistake in any of them moves every cusp.

1. Date of birth, day, month and year.
2. Local clock time as recorded, to the minute if you have it.
3. Place, ideally as coordinates. A town name is fine if the source shows you which coordinates it picked.
4. Time zone and daylight saving in force on that date. Some sources work this out from the place; others ask you for an offset from UTC. If you type an offset, use the one that applied on the birth date, not today's. Time zones and daylight saving covers the common slips, including double conversion.

The Ascendant moves through roughly a degree every four minutes on average, and much faster or slower depending on the sign rising and the latitude. An hour's time-zone error therefore shifts the cusps by many degrees, not a little.

Step 2: match the settings

• Zodiac: Tropical. A Sidereal setting moves every cusp by roughly 24° and usually changes its sign.
• House system: Placidus, the default on Astrologist.com. For a birthplace at an absolute latitude greater than 66° north or south, the free chart uses Equal houses from the Ascendant instead and says so on the chart; exactly 66° remains Placidus. Use whichever system your free chart names.
• Equal-house charts and the MC label: under that high-latitude fallback the wheel's MC and IC labels sit on the 10th and 4th cusps, which are not necessarily the true Midheaven and IC. If your source prints a separate MC, it can differ from the Equal 10th cusp. Chart angles at high latitudes explains why.
• Displayed precision: note whether the source shows degrees and minutes, minutes and seconds, or decimals, and whether it rounds or cuts off the last digit. The free chart's planet table cuts minutes off rather than rounding them.

Step 3: copy all twelve cusps

Copy cusps 1 to 12 with their signs, at the precision the source displays. Some sources list only the first six, or only the four angles. In both Placidus and Equal houses, each cusp is exactly opposite the cusp six houses on: the 7th is opposite the 1st, the 8th opposite the 2nd, and so on to the 12th opposite the 6th. Same degree and minute, opposite sign. You can fill in the missing six that way, and if your source does list all twelve, the opposite pairs are a quick check that you copied them correctly.

Four angles alone are not enough. Placidus cusps between the angles are not evenly spaced, so the 2nd, 3rd, 5th, 6th, 8th, 9th, 11th and 12th cusps cannot be worked out from the angles by simple division.

Step 4: run a coarse check against the free chart

Open your free birth chart with the same data. The Rising sign it names should be the sign of your source's 1st cusp. On the wheel, the house numbers should run in the same order your table does, and each planet's tick mark on the inner ring should fall in the same numbered sector your table puts it in, as far as the eye can tell.

This check catches the big errors: a wrong time zone, an a.m./p.m. slip, a Sidereal setting, the wrong house system. It does not verify the degrees. Two calculations can agree on the Rising sign and still put the Ascendant several degrees apart, and a source matching only your Rising sign is not numerically the same chart. Rounding and calculation conventions can produce differences between sources. When two sources disagree, check the birth data, time zone and settings first, and investigate any remaining discrepancy before relying on a cusp that falls close to a planet.

A worked cusp table

Lotte is a fictional person. Her chart was calculated with the same routines that draw the free chart, for Utrecht, the Netherlands (52.0907° N, 5.1214° E), on 27 August 1991 at 06:55 local time. The Netherlands was on summer time, UTC+2, so that is 04:55 UTC. Tropical zodiac, Placidus houses, Virgo rising. Longitudes are given to 0.01°, the precision the calculation code returns; the sign positions show whole minutes with the remainder cut off, as on the free chart's planet table.

Three things are worth noticing. The widths run from 20.34° to 38.49°, so no house is "30° wide" except by coincidence. The opposite pairs have identical widths, which is how Placidus houses are built. And the 8th house runs from 25°04' Pisces across 0° Aries to 21°46' Aries; one house can span the start of the zodiac.

A source that rounds to the nearest minute would show the 2nd cusp as 25°05' Virgo, because 25.08° is 25°04.8'. A one-minute difference of that kind is display, not disagreement.

Placing any degree in a house

Each house runs from its own cusp up to the next cusp, counting forward through the signs. The rule used on these pages:

• Start inclusive, next cusp exclusive. A longitude exactly on a cusp belongs to the house that begins there. A longitude a hair short of the next cusp is still in the earlier house.
• Count round the circle. For the house between cusp A and the next cusp B, work out how far the degree is past A and how wide the house is, both counted forward: subtract, and add 360° if the result is negative. The degree is in that house if its distance past A is less than the width.

Worked placements in Lotte's chart:

1. 10°00' Aries (10.00°). The 8th house starts at 355.08° and is 26.69° wide. 10.00 − 355.08 = −345.08; add 360 and the degree is 14.92° past the 8th cusp. That is less than 26.69°, so 10° Aries is in her 8th house. Plain subtraction without the wrap would have failed here.
2. Her Sun, 3°26' Virgo (153.44°). It is 1.30° short of the 1st cusp, so it sits at the end of the 12th house, even though it is in the same sign as her Ascendant.
3. Her Moon, 24°36' Pisces (354.61°). It is 0.47° short of the 8th cusp at 355.08°, so it is in the 7th. The margin depends on the birth time: with the same birth data at 06:52, three minutes earlier, the calculation puts the 8th cusp at 354.48° and the Moon, at 354.58°, inside the 8th. How accurate a birth time needs to be covers that kind of test.
4. Exactly 21.77°. That is the 9th cusp itself, so it belongs to the 9th house, not the 8th.

When display rounding decides nothing. The 8th cusp displays as 25°04' Pisces, which with cut-off minutes covers anything from 355.067° to just under 355.083°. A planet also displayed as 25°04' Pisces could be on either side of the cusp. Equal-looking numbers are not proof of equality: go back to a source with more precision, or report the placement as too close to call at this precision.

No margin is added before a cusp on these pages. Some astrologers start reading a planet as part of the next house a few degrees early; that is a convention some use, and the guides here work from the cusp itself.

Where the cusp table gets used

• Transits: a moving planet is compared with your fixed natal cusps. Transits through the houses shows how, with Lotte's chart as the example, and the planet guides start from Saturn transits through the houses.
• Your own placements: a natal planet within a degree or so of a cusp is worth checking numerically before you read the house pages in the Houses library.
• House rulers: the sign on each cusp gives the house its ruler, explained in house rulers explained.
• The Ascendant degree: what the exact degree adds to your Rising sign is covered in Ascendant degree vs Rising sign.

If you want to talk through what a borderline house placement could mean once you have the numbers, Ask the Astrologist can discuss the natal chart calculated on this site.

Related articles

• Astrology Houses Overview
• House Meanings in Astrology
• Ascendant Degree vs Rising Sign
• Chart Angles at High Latitudes
• Transits Through the Houses
• Synastry House Overlays