Old books give Mercury two bad grades in Pisces. It is in detriment there, and it is in fall there too. No other planet carries both weak grades in one sign. So you would guess that the sky keeps Mercury out of Pisces, or rushes it through. I checked that guess against 800 years of planet positions. It does not hold.
Over 1600 to 2400, Mercury spends 8.24 percent of all time in Pisces. That is close to a fair share of one sign in twelve. It is more time than Mercury spends in Gemini, one of its own home signs. The weak grades say something about style. They say nothing about how common the placement is.
The real Pisces story is in the calendar. In some years Mercury crosses the sign in about 16 days. In other years it turns back inside the sign and stays for more than two months. This page gives the counts, the dates from 2020 to 2030, and the method, so you can check my work.
Two weak grades in one sign
In traditional astrology, each planet has a home sign, called its domicile, and a sign of honor, called its exaltation. The sign across from the home is its detriment, a place where it works far from home. The sign across from the exaltation is its fall, a place of low standing.
Mercury is the odd one out. It rules Gemini and Virgo, and it is exalted in Virgo as well. Virgo is both its home and its place of honor. So the sign across from Virgo, which is Pisces, gets both weak grades at once. Mercury is the only one of the seven classical planets whose home and honor share a sign. That is why Pisces is the only place in the zodiac with a double weak grade.
Our page on Mercury in Virgo measures how often that double title actually occurs.
Venus runs the same axis the other way, and our page on Pisces and Virgo compatibility counts how many couples carry both halves of that swap.
Here is how the two main sources put it. Ptolemy, in the Tetrabiblos, book 1, chapter 19, writes in the Robbins translation that Mercury, being drier, “naturally is exalted, as it were, in Virgo, in which the dry autumn is signified, and is depressed in Pisces.” Depressed is his word for fall. Pisces is a water sign, the wrong climate for a dry planet.
Ptolemy names the fall, but he uses no word for detriment. The detriment tables reach us through later authors. William Lilly, in Christian Astrology, published in 1647, prints both grades in one line. In book 1, chapter 13, page 76, he writes that Mercury “hath Gemini and Virgo for his Houses, and is exalted in the 15 of Virgo: he receives detriment in Sagittarius and Pisces, his fall is in Pisces.”
Our page on the Pisces sign covers what this means for people with the Sun in Pisces. Here I look at a different question. Does the double weak grade change how common Mercury is in Pisces, or how it moves there?
Does the worst sign get less time? No
If the grades had a physical side, Mercury would spend less time in Pisces than in its home signs. I measured the share of all time that Mercury spends in each sign, from 1600 to 2400. A fair share would be 8.33 percent per sign.
| Sign Mercury is in | Share of all time, 1600 to 2400. |
| Sagittarius, its detriment | 9.09 percent, the most of any sign. |
| Scorpio | 9.03 percent. |
| Capricorn | 8.96 percent. |
| Libra | 8.81 percent. |
| Aquarius | 8.65 percent. |
| Virgo, its home and honor | 8.45 percent. |
| Pisces, its detriment and fall | 8.24 percent. |
| Leo | 8.02 percent. |
| Aries | 7.88 percent. |
| Cancer | 7.68 percent. |
| Taurus | 7.63 percent. |
| Gemini, its other home | 7.57 percent, the least of any sign. |
Look at the two ends. The sign with the most Mercury time is Sagittarius, one of its two signs of detriment. The sign with the least is Gemini, one of its two homes. Pisces sits in the middle of the pack. For comparison, Mercury in Capricorn, a sign where it holds neither grade, gets 8.96 percent. The grades and the time share do not line up at all.
Our page on Mercury in Gemini times each crossing of that sign and explains why a few long years hold most of its natives.
The real cause is the shape of Mercury’s path. Its orbit is the most lopsided of the planets. It swings close to the Sun on one side and far out on the other. The close side faces the part of the sky we call Gemini, so Mercury rushes through there. The far side faces Sagittarius, so it slows down there. Pisces is at neither end, so it gets a middle share.
I checked whether the answer holds over shorter spans. Century by century, the Pisces share runs from 8.15 to 8.37 percent. Over 1950 to 2010 it is 8.18 percent. So the result is steady. The double weak grade is a matter of meaning, not of numbers.
Who is born with Mercury in Pisces
Seen from Earth, Mercury never strays far from the Sun. Across the 800 years, the widest gap I found was 27.79 degrees. Lilly put the limit at about 27 degrees. A sign is 30 degrees wide. So with Mercury in Pisces, the Sun can only be in Aquarius, Pisces or Aries.
In date terms, for births from 1900 to 2100, Mercury in Pisces only occurs from 30 January to 18 April. A birthday outside that window rules it out. Inside the window, it depends on the year.
Here is the split, as a share of all the time Mercury spends in Pisces over the 800 years.
| Sun sign at birth | Share of people with Mercury in Pisces. |
| Sun in Pisces | 48.9 percent of them. |
| Sun in Aries | 37.0 percent of them. |
| Sun in Aquarius | 14.1 percent of them. |
| Any other Sun sign | Zero, it cannot happen. |
So more than half of the people with this placement are not Pisces Suns. More than a third are Aries. If that is you, compare this page with the one on Mercury in Aries, the sign your Sun is in. The same method, applied one sign back, is set out on the page about Mercury in Aquarius.
One more fact on this. The widest Mercury gap of all 800 years falls in this sign. It is 27.79 degrees, on 4 April 2355, with Mercury in Pisces in the morning sky. Most of the time, Mercury in Pisces rises before the Sun. It is on that morning side 63.0 percent of the time.
Three kinds of Pisces year
About three times a year, Mercury seems to stop and move backward for three weeks. Astrologers call this retrograde motion. It is a trick of view, like a slower car that seems to slide back as you pass it on the road. When one of these backward loops falls in Pisces, the stay changes shape.
Mercury passes through Pisces once a year. I sorted all 800 yearly stays from 1600 to 2400 into three kinds.
| Kind of stay | How common | How long it lasts. |
| Straight through, no loop | 61.8 percent of years | 15.6 to 19.9 days, with 16.4 days as the middle value. |
| Whole loop inside Pisces | 13.8 percent of years | 65.7 to 67.8 days in the sign without a break. |
| Loop dips out and back | 24.5 percent of years | Two visits over 55 to 68 days, with 20 to 66 days in the sign. |
In the last kind, Mercury enters Pisces, backs out into Aquarius, or runs ahead into Aries and backs in. Then it comes through again. So a stay can be cut in two, with a gap of days or weeks in the middle.
This matters for birth charts. In a loop year, the Pisces window can be four times as wide as in a straight year. So far more births in that year get the placement.
Is Mercury backward in Pisces more than elsewhere?
You might guess that Mercury likes to turn back in Pisces, in late winter. I tested it three ways, over the full 800 years. The answer is no. Pisces is an average sign for this.
| Test | Pisces | All signs. |
| Share of yearly stays with a backward loop | 38.3 percent | 30.1 percent in Gemini up to 44.6 percent in Sagittarius, 38.1 on average. |
| Share of backward turns that start in the sign | 8.6 percent | 8.3 percent would be a fair share. |
| Share of time in the sign spent moving backward | 19.5 percent | 19.2 percent over the whole zodiac. |
Pisces ranks seventh of the twelve signs for loop years. The late winter link is real, but only because Mercury is in Pisces in late winter at all. Of the 2,522 backward turns in the 800 years, 218 began in Pisces. That is one every 3.7 years on average.
What stands out is the rhythm. Loop years come in runs of two or three years in a row. Then come four years with no loop, or, rarely, five. Over the 800 years there were 64 runs of three and 57 runs of two. The pattern comes from Mercury’s cycle. Its backward loops repeat about every 116 days, so each year they land a bit earlier in the sign. After about seven years, they come back to the same place.
From 2020 to 2030, the loop years in Pisces are 2020, 2025, 2026 and 2027. The next runs are 2032 to 2033, and 2038 to 2040.
Every Mercury in Pisces from 2020 to 2030
All times are in UTC, the world clock. Check your birth time against it, since a date can shift by one day in your time zone. The minutes match JPL Horizons, the NASA ephemeris, to within five minutes.
| Year | Mercury in Pisces | What happened. |
| Year 2020 | 3 Feb 11:37 to 4 Mar 11:10, and 16 Mar 07:42 to 11 Apr 04:48 | Turned back at 12°53′ Pisces on 17 Feb, ahead again at 28°13′ Aquarius on 10 Mar. |
| Year 2021 | 15 Mar 22:26 to 4 Apr 03:41 | Straight through in 19.2 days. |
| Year 2022 | 10 Mar 01:32 to 27 Mar 07:44 | Straight through in 17.3 days. |
| Year 2023 | 2 Mar 22:51 to 19 Mar 04:23 | Straight through in 16.2 days. |
| Year 2024 | 23 Feb 07:27 to 10 Mar 04:02 | Straight through in 15.9 days. |
| Year 2025 | 14 Feb 12:06 to 3 Mar 09:02, and 30 Mar 02:16 to 16 Apr 06:25 | Turned back at 9°35′ Aries on 15 Mar, ahead again at 26°50′ Pisces on 7 Apr. |
| Year 2026 | 6 Feb 22:47 to 15 Apr 03:21 | Whole loop inside, back at 22°34′ Pisces on 26 Feb, ahead at 8°29′ Pisces on 20 Mar. |
| Year 2027 | 1 Feb 01:26 to 18 Feb 12:17, and 18 Mar 10:02 to 8 Apr 23:20 | Turned back at 5°59′ Pisces on 9 Feb, ahead again at 20°55′ Aquarius on 3 Mar. |
| Year 2028 | 13 Mar 07:07 to 31 Mar 12:28 | Straight through in 18.2 days. |
| Year 2029 | 6 Mar 18:15 to 23 Mar 12:18 | Straight through in 16.8 days. |
| Year 2030 | 27 Feb 08:58 to 15 Mar 08:41 | Straight through in 16.0 days. |
Note the contrast. In 2026, Mercury stayed 67.2 days. In 2024, it stayed 15.9 days. A baby born in February or March 2026 was far more likely to get this placement than one born in the same weeks of 2024.
Watch the gaps too. Someone born on 1 March 2027 has Mercury back in Aquarius, even though the date sits between two Pisces visits. Someone born on 20 March 2025 has Mercury in Aries, for the same reason.
Born with Mercury moving backward
Of all the time Mercury spends in Pisces, 19.5 percent is spent moving backward. So about one person in five with this placement was born during a loop. That is the same rate as for Mercury as a whole. Our guide to retrograde planets in the natal chart explains how that is read.
Lilly wrote that Mercury is backward for 24 days. I measured every loop from 1600 to 2400. They last from 19.8 to 24.2 days, with 22.5 days as the middle value. For loops that begin in Pisces, the range is 21.4 to 23.1 days. So Lilly gave close to the upper bound, not the usual length.
In the old view, a backward Mercury turns its work inward. For a Pisces Mercury, already a planet away from home, that can mean a mind that thinks things through in private before it speaks. The chart as a whole decides how that plays out.
How the tradition reads Mercury in Pisces
Mercury stands for the mind, for speech, trade and learning. Pisces is a water sign, mutable, which means it sits at the end of a season and bends with change. Mercury likes clear edges and names. Pisces blurs edges. That clash is the old reason for the weak grades.
A weak grade does not mean a weak mind. It means Mercury works in a room it does not own. In a traditional chart, the owner of that room is Jupiter, the ruler of Pisces. Modern astrologers add Neptune as a second ruler. So the first thing to check is where Jupiter is, and how well it is placed. A strong Jupiter gives Mercury a good host.
There is a neat twist here. Jupiter rules Pisces and is in detriment in Virgo and Gemini, the signs Mercury rules. If you have Mercury in Pisces and Jupiter in Virgo or Gemini, the two planets sit in each other’s signs. That is called mutual reception. Each planet is weak where it stands, yet each is host to the other, and the tradition reads that as a kind of trade.
The same cross tie joins two Sun signs, and our page on Pisces and Gemini compatibility shows how it plays out between two partners.
Where this placement shows in daily life depends on the house. In the third house, it colours how you learn and talk. In the tenth, it colours your work. Psychological writers such as Liz Greene and Stephen Arroyo read a sign as a style of expression, not a verdict. In this sign, the style is one of images, mood and pattern, more than lists and rules.
In practice, people with this placement do well to put key facts in writing. The mind catches the tone of a talk with ease. The dates and figures slip past. A short note after a call keeps both halves.
The method, so you can redo it
A number no one can check is worth nothing. Here is how I got these.
I used the astronomy-engine library. For each moment, I took the apparent place of Mercury and the Sun, seen from the centre of the Earth. I turned each into a tropical longitude, measured along the path of the Sun from the spring equinox of that date.
For the stays, I stepped through time every six hours from 1 January 1600 to 1 January 2400. Each time Mercury changed sign or turned, I halved the step until the moment was exact to well under a second. Then I added up the exact time in each sign, and in each sign while moving backward. I merged two visits into one stay when the gap was under 60 days. That gave 2,522 backward turns and 800 stays in Pisces.
For the check, I used a second route with no search at all. I took one position per day from JPL Horizons, the NASA ephemeris, over the same 800 years, and simply counted. Horizons gave 8.24 percent for Pisces, 19.5 percent of that time backward, and 38.35 percent of stays with a loop. The Sun sign split matched to 0.02 percent. For 2020 to 2030, I pulled Horizons positions every ten minutes. Every entry, exit and turn matched to within five minutes.
Why 800 years? Short windows can mislead. Mercury’s loops shift year by year, and the orbit turns slowly. A long window evens this out.
Frequently asked questions
Is Mercury in Pisces rare?
No. Over 1600 to 2400, Mercury spends 8.24 percent of all time in Pisces. That is more than in Gemini, 7.57 percent, which is one of Mercury’s own home signs.
Why is Mercury in detriment and fall in Pisces?
Pisces is across from Virgo. Virgo is both Mercury’s home and its sign of honor. So Pisces gets both weak grades. Lilly lists both in Christian Astrology, book 1, chapter 13.
How long is Mercury in Pisces each year?
About 16 to 20 days in a year with no backward loop there. In a loop year, the stay runs 55 to 68 days from first entry to last exit.
Does Mercury go retrograde in Pisces more than in other signs?
No. Over 800 years, 38.3 percent of Pisces stays hold a backward loop, close to the 38.1 percent average. Loop years come in runs of two or three, then four years without.
When is Mercury next in Pisces?
From 1 February 2027 at 01:26 UTC to 18 February, and again from 18 March to 8 April 2027, after a backward loop.
Can I have Mercury in Pisces if I am not a Pisces?
Yes, if your Sun is in Aries or Aquarius. Over 800 years, 37.0 percent of people with Mercury in Pisces have an Aries Sun, and 14.1 percent have an Aquarius Sun.
Go deeper with your own chart
A number is a start. Your chart is the rest. An Astrovision report reads your Mercury with its Sun, its house, its aspects and its host, Jupiter. It comes as a written guide and a personal podcast you can play on a walk. For the bigger picture, our guide to the zodiac signs explains how the twelve fit together.