Quick answer: Derived houses let you read another person inside your own chart. You treat the house that signifies them as their first house, then count the topic you want forward from that new first. A partner's money is their second house, which lands on your eighth. Nothing in the chart actually moves. The turning is purely a counting overlay.
One of the most elegant techniques in traditional and horary astrology is this: a single chart can describe far more than the person it was cast for. This technique is called derived houses, or turned houses. With it, you can read a partner's finances, a child's illness, or a parent's career, all without casting a second chart. You simply re-anchor your reading on the house that stands for that person, then count topics forward from there. Once the method clicks, your own twelve houses quietly contain everyone connected to you.
What Derived Houses Actually Are
A derived house is a conceptual overlay, not a new chart. To read another person inside your chart, take the house that signifies them and treat it as their first house, their personal Ascendant. From that new first house, count forward to whatever topic you want to read for them.
The key word is conceptual. You do not recalculate anything. The planets, the signs, and the house cusps never move. You are not casting a fresh chart or working out a new Ascendant. You are simply relabelling the wheel for the length of one reading, asking: "If this house were that person's first house, where would their money, their health, or their career fall?"
This matters because every house keeps its original meaning at the same time. Your eighth house is still your eighth house, with its own significations. When you turn the chart to read a partner, that same eighth house also becomes the partner's second house. The two layers coexist. You read them separately, depending on the question in front of you.
The Counting Rule That Keeps You Honest
The single most common beginner mistake is an off-by-one error. When you turn the chart, the base house itself counts as one. It becomes the derived first house, so you start counting on it, not on the house after it.
To find a partner's second house, begin on the seventh house (that is one) and step to the eighth (that is two). To find a child's sixth house, count the fifth house as one, then six, seven, eight, nine, ten, landing on your radical tenth. The base house always gets the number one.
If you would rather not count on your fingers, this formula gives the same answer every time:
derived = ((base + topic - 2) mod 12) + 1
Here "base" is the house that signifies the person, and "topic" is the house number of the subject you want to read for them. The formula simply counts topic minus one houses forward from the base. Some sources describe this count as "inclusive" and others as "not inclusive." Either way, once they offset by topic minus one, they all land on the same house. The label does not matter. The house does.
Partner's Money, Child's Illness, Parent's Career
These three turns are the classic worked examples, and each one teaches the method cleanly.
A partner's money is your eighth house. The spouse or partner is signified by the seventh house. Their money and resources are their own second house, which is the eighth house counting from the seventh (seventh is one, eighth is two). This is the age-old reasoning behind why the eighth house is linked to a partner's wealth, dowries, inheritance, and "other people's money" in general. Just remember that your radical eighth house keeps its own separate meanings of crisis and shared resources too. In derived terms, it is simply "the partner's second."
A child's illness is your tenth house. Children are signified by the fifth house. Illness and bodily affliction belong to the sixth house. Count six houses from the fifth (five, six, seven, eight, nine, ten) and you arrive at your radical tenth, which serves as the first child's derived sixth. Be precise here: the sixth is the traditional house of sickness and affliction, not of general health or vitality. Overall constitution is read from the first house and the Ascendant instead, so this turn targets the child's illnesses specifically, not their vitality as a whole.
A parent's career is the tenth house from that parent's house. Career and public standing belong to the tenth house. First decide which house signifies the parent, treat it as their first house, then count forward to their tenth. If you take the parent as the fourth house, counting ten houses forward (four, five, and around the wheel back to one) brings you to your radical first house, which becomes that parent's derived career house. This only works once you have fixed which parent is which, and that turns out to be a genuine fork in the road.
The Parent Problem and Whole-Sign Caveats
Astrologers do not agree on which parent the fourth house signifies. This is a real, unresolved difference between traditions, not a settled fact.
In genuinely Hellenistic astrology, the fourth house signified both parents together, and the tenth house carried no parental meaning at all. Parents were judged mainly from planetary significators instead: the Sun and Saturn for the father, the Moon and Venus for the mother, along with the relevant lots. The familiar split, father to the fourth house and mother to the tenth, is a later medieval and horary development, in which the fourth house came to mean roots, paternal lineage, and the family name. Most modern astrologers reverse even that, putting the mother in the fourth house as the home and nurturing parent, and the father in the tenth as the authority figure.
The practical lesson is simple: state your convention before you turn the chart. If you do not, "the father's career" could resolve to two different derived houses, and you will not know which one is right. There is also a structural caveat in whole-sign houses, where the IC and MC degrees (the exact points of the lower and upper angles of the chart) do not line up with the fourth and tenth house cusps. The Midheaven can fall in any whole-sign house from the eighth to the twelfth, so the angular degrees and the house-based parental signification can point in different directions.
Chaining Relatives Through the Wheel
Once you trust the counting rule, you can reach more distant relatives by chaining turns together. Siblings are signified by the third house, so every sibling-based relative is worked out through the third.
A sibling's child, your niece or nephew, is the fifth house from the third, which lands on your seventh house. A sibling's illness is the sixth house from the third, which lands on your eighth. Grandparents come from doubling a parent's house: under the father-as-fourth convention, the father's father is the fourth house from the fourth, which is your seventh house. Grandchildren follow the same logic as the fifth house from the fifth, landing on your ninth. Just do not assume your radical seventh house always "is" your nephew. It only stands for the nephew under this specific fifth-from-third derivation. Left untouched, the seventh house is still your partner and open enemies.
A word of caution closes the technique. Experienced traditional and horary astrologers cap turning at one step, or at most two. Signification dilutes fast as the chain lengthens, and something like "my cousin's spouse's money" stacks too many derivations to trust. Some traditionalists reject turned houses entirely and argue the radical chart is enough on its own. Treat derived houses as one recognised tool among several, not a universal rule, and never as a licence to map every distant relative. If you want to see your own houses laid out cleanly before you start turning them, cast a free birth chart and study the radical meanings first, then explore more techniques on the AstroAk blog.
Frequently Asked Questions
Do derived houses change my actual chart?
No. Turning the chart is purely a counting and interpretive overlay. The planets, signs, and house cusps never move, and you do not cast a new chart or recompute the Ascendant. You simply relabel one house as another person's first house for the length of a single reading, while every house keeps its original meaning at the same time.
Why is a partner's money the eighth house specifically?
Because the partner is signified by the seventh house, and their money is their own second house. Counting from the seventh as one, the eighth house is the second house from there. This derived logic is the classical reason the eighth house has long been tied to a partner's wealth, inheritance, dowries, and "other people's money," even though the radical eighth house also carries its own separate meanings of crisis and shared resources.
How far can I keep turning the chart?
Most practitioners stop after one turn, or two at the very most. Signification becomes diluted and unreliable as the chain grows, so something like "my cousin's spouse's money" stacks too many derivations to read with confidence. Derived houses are a genuine classical tool, but they are not infinitely recursive, and over-turning tends to produce spurious readings rather than real insight.
