How to build an astrology app in 2026: an engineer's guide

Two agencies priced the same kind of app this year. IMG Global Infotech says to expect a budget between $5,000 to $15,000+. Amar Infotech says a full astrology app costs $50,000 to $300,000. It puts a basic MVP, the smallest version you can ship, at $20,000-$40,000 over three to four months. The high estimate is 20 times the low one.

Search for the cost of an astrology app. The whole first page is agencies, and each one starts with a price. I took both quotes above from that page while writing this. Asking about price is fair. But these prices are not built on anything. So this guide shows what an astrology app is really made of. It shows which parts to buy and what it costs to run.

A real cost estimate starts from a spec. A spec is a written list of what the app must do. Neither page has one. So neither number comes from anything you can check. But both pages do list features. Those lists tell you more than the prices do.

What the cost guides leave out

IMG Global Infotech lists eight features an astrology app needs:

• User profiles
• Real-time horoscopes
• A kundli or birth chart generator
• Live astrologer chat
• Push notifications for planetary events
• A compatibility checker
• A tarot module
• A blog

The list itself is fine. The problem is that it treats all eight features as equal work. It makes the birth chart generator look as easy as the blog. It is not. A birth chart is a map of where the planets were at the exact time and place of a birth. A kundli is the Indian word for the same chart.

Seven of the eight are normal product features. You have built things like them before under other names. The eighth is different. Computing a birth chart is an astronomy problem with one correct answer. Your users can check your answer against every other app on their phone. Yet the guide never mentions the hard parts: ephemeris data, timezones, or house systems. An ephemeris is a table of where the planets are at any given moment.

Amar Infotech does name the problem. Its advice is worth quoting. Use reliable astrology APIs and hire experienced astrologers to verify calculations. An API is a service your own code calls over the web to get data or work done. Amar's suggested stack lists Swiss Ephemeris for the math. So the pricier guide tells you to buy the hard layer. Then it charges $50,000 to $300,000 for what is left.

That gap is the point of this guide. Nobody can tell you what an astrology app costs without a spec. But we can show what one is made of. And we can show which parts deserve your time.

Three layers, and only one is yours to build

Every astrology app breaks down into the same three layers.

The calculation layer turns a birth date, time, and place into planet positions. It also computes house cusps, the start points of the twelve houses, and the other values each tradition uses. The math is deterministic. That means the same input always returns the same output. So there is one right answer for everyone. Your competitor computes the same Moon position for the same birth moment. If not, one of you has a bug.

Above it sits the content layer. It turns those numbers into words. That means daily horoscopes, birth chart reports, match write-ups, and chat answers. All of it is generated. Some apps use banks of pre-written text tied to chart features. Others hand the computed chart to a language model.

On top sits the product layer. This is everything users see and feel as your app. It is how you ask a stranger for their exact minute of birth without losing them. It is what you send at 7am and what you hold back. It is what makes the app feel worth opening every day.

Every serious app must get the math right, so users just expect it. Correct math cannot make your app stand out. That is why you buy this layer instead of building it. The agency quotes send most of the hours to the wrong layer. A budget that treats all three layers as custom work pays full price for a solved problem.

Building the base layer yourself has real costs that the guides skip. Amar Infotech suggests Swiss Ephemeris but does not say what running it takes. Swiss Ephemeris is a code library with no service behind it. You keep its .se1 data files on disk. You keep their path correct across every deploy. You also own all the code on top. That includes timezone lookup and house math. It also includes the ayanamsha, the gap between the two zodiac systems, measured in degrees. And it includes the extra values each tradition expects.

Then there is the license, which cost guides rarely mention. Swiss Ephemeris comes with two license options. You follow the AGPL-3.0, a strict open-source license, or you buy a paid license from Astrodienst. The AGPL sets rules for network services built on the code. That means a talk with a lawyer, and no agency estimate I have read includes that cost. Teams already running it can compare the two paths in the Swiss Ephemeris migration guide.

Here is one honest note. In real code, the line between the content and product layers gets blurry. The voice of your text is a product decision that lives in the content layer. Teams that treat generated text as filler ship apps that read like filler.

Pick the system your users already read

Before you write any code, make one choice: sidereal or tropical. This choice sets your endpoints, your vocabulary, and half your UI. An endpoint is one URL in an API that does one job.

Western astrology uses the tropical zodiac, tied to the March equinox. Vedic astrology uses the sidereal zodiac, tied to the fixed stars. The two anchors have drifted apart over the centuries. That drift is the ayanamsha. The ayanamsha endpoint returns the number for any moment. For a 1990 birth date, the widely used Lahiri value is about 24.10 degrees.

Now do the math. A zodiac sign is 30 degrees wide. A sidereal position sits about 24 degrees behind the tropical one. The two systems agree only when the tropical position falls in the last six degrees of its sign. So they disagree about which sign a planet is in about four times in five.

Picture a user who reads Western horoscopes. Your app shows them a different Sun sign. They will not see it as a difference between two valid systems. They will see it as a bug. They will uninstall, and they will be right.

So match the system your audience already uses. Indian users, at home and abroad, expect sidereal charts. They expect nakshatras (27 divisions of the sky used in Vedic astrology) and dashas (planet-ruled time periods used for forecasts). They also expect kundli matching. North American and European users expect tropical charts, Placidus houses, and aspects, the angles between planets. The API keeps the two systems on separate paths. So the choice stays visible in your code instead of hidden in a config flag. planets returns sidereal positions. planets/tropical and house_cusps/tropical return the Western versions.

The choice shapes more than the sign math. Each tradition gives you different things to show. A sidereal app gets nakshatras and dasha periods. Dasha periods give you a timeline widget and a reason to send notifications. A sidereal app also gets kundli matching, the most proven paid astrology feature in the Indian market. A tropical app gets aspects, house patterns, and charts that compare today's sky to the birth chart. Those call for a different kind of daily content. Adding the other system later usually means rebuilding your data model. So decide early.

Serving both audiences is cheap, because the birth data is the same. Store it once, compute twice, and let the user pick a system. The guide on ayanamsha, house systems, and why charts differ explains why two correct charts of the same person can disagree. The astrology glossary defines the words your product copy will need.

The calculation layer in code

Here is the whole layer at work. Birth data goes in and a chart comes out. The code is shorter than the paragraph that describes it.

The API checks who you are with HTTP Basic auth. Your user ID is the username and your API key is the password. There is a second mode too. A wallet-backed access token goes in an x-astrologyapi-key header. Use that one if you pay per call instead of by subscription. The guide on access tokens versus user ID and API key explains which to pick.

// Server-side only. json.astrologyapi.com sends no CORS headers,
// and a key shipped to the browser is a leaked key.
const AUTH =
  'Basic ' +
  Buffer.from(
    `${process.env.ASTROLOGY_USER_ID}:${process.env.ASTROLOGY_API_KEY}`,
  ).toString('base64')

async function call(endpoint, body) {
  const response = await fetch(`https://json.astrologyapi.com/v1/${endpoint}`, {
    method: 'POST',
    headers: { Authorization: AUTH, 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  })
  if (!response.ok) {
    // Fail loudly. A half-computed chart is worse than no chart.
    throw new Error(`${endpoint} ${response.status}: ${await response.text()}`)
  }
  return response.json()
}

// The eight fields every chart endpoint takes. The first five are
// integers; lat, lon and tzone are floats.
const birth = {
  day: 22, month: 7, year: 1992,
  hour: 9, min: 21,
  lat: 25.31668, lon: 83.01042, tzone: 5.5,
}

const [planets, details] = await Promise.all([
  call('planets', birth),       // one entry per body, plus the ascendant
  call('astro_details', birth), // ascendant, moon sign, nakshatra, tithi
])

details.ascendant  // "Leo"
planets[0].sign    // "Gemini"

// isRetro is the STRING "true"/"false" on the nine planets and a real
// boolean on the ascendant entry. Compare it; do not truth-test it.
const retrograde = planets.filter((p) => p.isRetro === 'true')

Every chart endpoint takes the same eight fields: day, month, year, hour, min, lat, lon, and tzone. Learn those eight and you can call most of the API.

planets returns an array rather than an object. It has one entry per body, from the Sun through Ketu. The ascendant comes last. The ascendant is the zodiac sign rising in the east at the birth moment. Each entry carries its sign, sign lord, nakshatra, nakshatra lord, house, and degree. astro_details adds the chart-level facts: ascendant name, moon sign, tithi, yog, karan. Tithi, yog, and karan are values from the Vedic calendar.

Two calls inside one Promise.all give you enough to render a chart. The birth chart app guide for Next.js builds the full page, with a form, error states, and a results table. If you want a drawn chart wheel instead of raw fields, call horo_chart/:chart_id. It takes the same eight fields plus a chart id. D1 is the birth chart and D9 is the navamsha, a second chart used in Vedic astrology.

The sample code runs on the server on purpose. The API host sends no CORS headers, so browsers block direct calls from a web page. Even if a browser call worked, it would show your key to anyone with developer tools open. Put the key in a server-only environment variable. Do not use any prefix that exposes it to the client bundle.

Timezones cause most wrong charts

If your app ever ships a wrong chart, the timezone offset is almost always why. The planet math is rarely the problem.

The bug has one common shape. A developer needs a UTC offset, the gap in hours between a place and universal time. The browser offers one, so the developer uses it. But that offset describes where the user is sitting right now, in the current season. The chart needs the offset that applied at the birth place on the birth date. That can be a different number.

Take a user born in New York in December who opens your app in July. Their browser reports -4 for daylight time. The birth needed -5. Nothing errors and nothing logs. The chart is simply off by a full hour. Old birth dates make it worse. Timezone rules change over time, so the offset a place used decades ago is not always the one it uses now.

An hour is a big error here. Earth turns about 360 degrees in 24 hours. So the ascendant moves about one degree every four minutes. An hour of error moves the rising degree by about fifteen degrees. That is half a sign. The rising sign, the house cusps, and everything that rests on them can shift. Your app draws all of it cleanly and with confidence. And the chart belongs to the wrong moment.

The fix is to resolve the offset on the server, in this order.

// 1. Place string -> coordinates and an IANA zone id.
const { geonames } = await call('geo_details', { place: 'mum', maxRows: 2 })
const place = geonames[0]
// { place_name: 'Mumbai', latitude: 19.07283,
//   longitude: '72.88261', timezone_id: 'Asia/Kolkata' }
// Note: latitude comes back as a number, longitude as a string.

// 2. Coordinates plus the BIRTH date -> the offset in force that day.
//    Date format is MM-DD-YYYY. This is the birth date, not today.
const { timezone } = await call('timezone_with_dst', {
  latitude: place.latitude,
  longitude: Number(place.longitude),
  date: '06-27-2000',
})

// 3. Only now compute the chart.
const chart = await call('planets', {
  day: 27, month: 6, year: 2000,
  hour: 14, min: 15,
  lat: place.latitude,
  lon: Number(place.longitude),
  tzone: timezone,
})

First geocode the place, which means turning its name into map coordinates. Then resolve the offset for the birth date. Only then compute the chart. Never take this value from the client. And never ask the user to type an offset into a number field. That is the same bug, just typed by hand. The timezones, DST, and historical birth data guide goes deeper. It covers the old rule changes that cause the most wrong charts.

One related problem has no clean technical fix. Many users do not know their birth time. You cannot compute an ascendant without it, and no code can create missing information. What you can do is design for it honestly. Show a smaller chart built from date and place alone. Do not show a confident chart built on a guessed noon. Handling an unknown birth time covers the patterns that work.

The content layer is generated text

Once the positions are computed, everything users read is a rendering problem. The content splits into three shapes. Each shape has a different cost to run, so treat them separately.

Sign-level daily content is the cheapest thing you will ever ship. sun_sign_prediction/daily/:sign returns a prediction split into personal_life, profession, health, emotions, travel, and luck. There are twelve signs. So a full day of content for every user costs twelve calls, made once, on a schedule. Call it per pageview instead and you pay for the same twelve responses thousands of times. The Telegram horoscope bot guide is a complete working build on this endpoint.

Chart-level reports are what people pay for. The PDF report endpoints take the birth fields plus a set of branding fields: logo_url, company_name, company_info, domain_url, company_email and footer_link. They return a hosted pdf_url. This is how you white-label, which means selling the report under your own brand. The PDF shows your name and logo, and ours appears nowhere. Generating your first PDF report shows the full request step by step.

Chat content carries the biggest risk. A language model will answer a chart question whether or not it has a chart. It can get your Sun sign right from the date alone, and it sounds confident doing it. But moon sign, ascendant, and house cusps need an ephemeris. A model without one makes up numbers that only look real. The fix is not exciting. Compute the chart first. Hand the model the computed JSON. Let it explain only what it was given. Grounding an LLM on real chart data shows the tool-use setup.

One warning applies to all three shapes. Raw API text published as-is is thin content, and search engines have been good at spotting thin content for years. Generated text is raw material rather than a finished article. Your framing, your voice, and your point of view make it worth reading. None of those come out of an endpoint.

What a first version costs to run

Set the build quote aside for a moment. Price the cost that repeats every month instead. That number decides whether you can charge users more than you spend.

Every new account starts with 150 free credits. That is enough to build and test a full integration before you pay anything. After that there are two ways to pay. A wallet holds a credit balance, and each call draws from it. The minimum top-up is $5 on a USD wallet or ₹50 on an INR one. Or you subscribe to a suite. The Vedic suite starts at $29 or ₹1,500 a month. Western starts at $49 or ₹2,999. Horoscope feeds start at $89 or ₹3,500.

Here is the honest limit, and it is a real one. I cannot give you a cost per user. Credit cost varies by endpoint. A geocoding lookup, a planet position call, and a generated PDF draw different amounts. An invented average would look exact and be wrong. The API pricing catalog lists the current cost per endpoint. Model your own traffic against it before you set a price. And read pay as you go with a wallet to see how spend is tracked.

What you can control is call volume, and caching can cut it to a tenth or less. Two facts make caching easy here. A birth chart never changes for a fixed birth date, time, and place. So you can cache it forever, keyed on those birth details. A daily horoscope is the same for everyone with the same sign. So it caches on (sign, date).

A horoscope feature serving a hundred thousand users can run on twelve calls a day. The same feature calling the API per pageview cannot. The whole difference is your cache layer.

Scope follows the same logic. A first version needs exactly three things. It needs a birth-data flow that produces a correct timezone. It needs a computed chart shown clearly. And it needs one repeating reason to come back, usually the daily feed.

Everything else on the agency feature list can wait. The two priciest items can wait the longest: live astrologer chat and a tarot module. Live chat is a two-sided marketplace. It needs astrologer recruiting, scheduling, payouts, and moderation. That is a second business in itself. It does not belong in a build whose only job is to test whether anyone wants the first one.

Spend the time you save on the birth-data screen. It is the most important screen you will build. It is the one place where a product choice decides whether the math comes out right. A place autocomplete backed by geocoding gives you coordinates and a timezone you can resolve. A free-text city field gives you a support queue. Getting that screen right does more for chart accuracy than anything after it.

Now compare that to the twenty thousand dollar MVP. A working prototype takes a weekend and the free credits. It can capture birth data, resolve the timezone, compute a real chart, and show it. So you can test the idea with real users before you spend anything. The agency quote asks you to decide first, in a meeting.

None of this makes the agency number a scam. Live astrologer marketplaces, payment flows, moderation, and native apps on two platforms cost real money. A team that has built one before is worth paying. The problem is the order. Do not buy the expensive version before you have proof that anyone wants the cheap one.

Before you ship

Here is a short list. The common failures are boring and well known.

• Keep keys in server-side environment variables. No API credential should ever reach the client bundle.
• Retry only on 5xx responses and network errors. A 401 from a wrong key fails the same way forever, and a 400 from a bad date does too. Retrying either one wastes credits to repeat a known result.
• Give every request a timeout. A hung connection should never block a page render.
• Cache birth charts and daily horoscopes before launch. Do not wait for the first invoice.
• Test timezone resolution with a birth date from a different daylight saving period than today. That is the case tests usually miss.

Going to production: credits, errors, caching expands each item with code, and the pricing page has the current plan details.

The main thing to take away is the order of work. The calculation layer is a solved problem, and you can connect it in an afternoon. That frees the budget the agency guides assign to it. Spend it on the layer nobody can sell you. That layer is the reason someone opens your app on a Tuesday morning. Eleven other apps can compute the same chart. Yours needs a reason of its own.