Due Date Calculator API

GET

Build complete pregnancy timelines from a single date.

Due Date Calculator estimates pregnancy due dates using either last menstrual period or conception date, providing comprehensive pregnancy timeline information.

Try it — live request, no key required

Request

GETapi.apiverve.com/v1/duedatecalculator?last_period=2025-06-01

Query parameters

last_periodstring

Verification

Format

No key required to try it. Get a key to use it in your app.

Example

{
  "status": "ok",
  "error": null,
  "data": {
    "calculation_method": "last_period",
    "last_period_date": "2025-06-01",
    "estimated_conception_date": "2025-06-15",
    "due_date": "2026-03-08",
    "current_progress": {
      "days_pregnant": 474,
      "weeks_pregnant": 67,
      "days_into_week": 5,
      "formatted": "67 weeks, 5 days",
      "trimester": 3,
      "percentage_complete": 169.29
    },
    "time_until_due": {
      "days": 0,
      "weeks": 0,
      "days_extra": 0,
      "formatted": "Past due date",
      "is_overdue": true
    },
    "upcoming_milestones": [],
    "important_dates": {
      "end_first_trimester": "2025-08-31",
      "end_second_trimester": "2025-12-07",
      "full_term_begins": "2026-02-15"
    },
    "disclaimer": "This is an estimate only. Due dates can vary. Consult your healthcare provider for medical advice."
  }
}

About the Due Date Calculator API

Includes pregnancy milestones, percentage completion, and important dates like trimester transitions, perfect for pregnancy tracking and prenatal care applications.

What people use it for

Pregnancy Tracking: Build pregnancy tracking applications with accurate due date calculations based on last menstrual period or conception date
Prenatal Care: Calculate gestational age for prenatal care appointments, monitoring fetal development, and scheduling medical tests
Maternity Planning: Create maternity planning tools with delivery date estimates, trimester breakdowns, and important date tracking
Milestone Tracking: Provide pregnancy milestone information with week-by-week pregnancy timeline and key development stages

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON: Default REST response
XML: Markup format
YAML: Human-readable
CSV: Tabular export
GraphQL: Query language
MCP: For AI agents

View all integrations →

Other ways to use Due Date Calculator

Same data, same APIVerve account, same credit balance — one key works on all of them.

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.on VerveKit Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.on VerveSheets Ground an agent on itA cited, machine-checkable fact your model can't produce on its own.on VerveContext

Questions.

Common questions about the Due Date Calculator API.

Read the docs →

Can I calculate due dates using either last period or conception date?

Yes. The API provides dedicated endpoints for both methods, accepting either the first day of the last menstrual period or the conception date to generate the delivery estimate.

What milestone dates does the timeline provide?

Every plan provides the estimated due date; paid plans also include the end dates for the first and second trimesters, the date full term begins, and a list of upcoming pregnancy milestones.

How far does the Starter plan go for due date calculations?

Starter covers 100,000 due date calculations each month. Each request uses 2 credits, which works out to about $0.30 per 1,000 calls. The Free plan includes 100 calculations per month.

Are trimester transition dates and progress metrics included on the Free plan?

No. The Free plan returns the estimated due date and calculation method, but detailed progress metrics, trimester end dates, full-term dates, and milestone lists are premium fields available on any paid plan.

What date format do the endpoints accept?

Both endpoints require dates submitted in standard ISO format as YYYY-MM-DD. Providing dates in other structures will prevent the calculation from processing.

Request parameters — GET /v1/duedatecalculator

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Parameter	Type	Example	Description
`last_period`Required	string	`2025-06-01`	First day of last menstrual period (YYYY-MM-DD) date

Example request

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curl "https://api.apiverve.com/v1/duedatecalculator?last_period=2025-06-01" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Header	When	Value
`x-api-key`Required	Every request	Your API key. Header names are case-insensitive, so `X-API-Key` is the same header.
`Authorization`Alternate	Instead of the above	`Bearer <key>` — for clients that only expose bearer auth. Resolves to the same account and the same billing.

401 is the only auth verdict

A 401 means the key is missing, invalid or expired. A 403 means the key is valid but not permitted here — blocked by a key restriction or an IP allow-list. Running out of credits is a 429.

Response — GET /v1/duedatecalculator

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

Sample response

{
  "status": "ok",
  "error": null,
  "data": {
    "calculation_method": "last_period",
    "last_period_date": "2024-01-01",
    "estimated_conception_date": "2024-01-15",
    "due_date": "2024-10-07",
    "current_progress": {
      "days_pregnant": 715,
      "weeks_pregnant": 102,
      "days_into_week": 1,
      "formatted": "102 weeks, 1 days",
      "trimester": 3,
      "percentage_complete": 255.36
    },
    "time_until_due": {
      "days": 0,
      "weeks": 0,
      "days_extra": 0,
      "formatted": "Past due date",
      "is_overdue": true
    },
    "upcoming_milestones": [],
    "important_dates": {
      "end_first_trimester": "2024-04-01",
      "end_second_trimester": "2024-07-08",
      "full_term_begins": "2024-09-16"
    },
    "disclaimer": "This is an estimate only. Due dates can vary. Consult your healthcare provider for medical advice."
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`calculation_method`	string	`"last_period"`	Method used for calculation: last_period or conception_date
`last_period_date`Premium	string	`"2024-01-01"`	First day of last menstrual period in ISO format
`estimated_conception_date`Premium	string	`"2024-01-15"`	Estimated conception date calculated from last period
`due_date`	string	`"2024-10-07"`	Estimated delivery date in ISO format
`current_progress`	object	`{...}`	How far along the pregnancy is today, in days and weeks
`days_pregnant`Premium	number	`715`	Total number of days pregnant
`weeks_pregnant`Premium	number	`102`	Number of complete weeks of pregnancy
`days_into_week`Premium	number	`1`	Additional days beyond complete weeks
`formatted`Premium	string	`"102 weeks, 1 days"`	Human-readable pregnancy duration with weeks and days
`trimester`Premium	number	`3`	Current trimester number: 1, 2, or 3
`percentage_complete`Premium	number	`255.36`	Pregnancy completion percentage relative to due date
`time_until_due`	object	`{...}`	How long until the due date, with a formatted summary
`days`Premium	number	`0`	Complete days remaining until due date
`weeks`Premium	number	`0`	Complete weeks remaining until due date
`days_extra`Premium	number	`0`	Additional days beyond complete weeks remaining
`formatted`Premium	string	`"Past due date"`	Human-readable time remaining until delivery
`is_overdue`Premium	boolean	`true`	Whether pregnancy has passed the due date
`upcoming_milestones`Premium	array	`[]`	Array of upcoming pregnancy milestones and dates
`important_dates`	object	`{...}`	Key milestones: the end of each trimester and viability
`end_first_trimester`Premium	string	`"2024-04-01"`	Estimated end date of first trimester
`end_second_trimester`Premium	string	`"2024-07-08"`	Estimated end date of second trimester
`full_term_begins`Premium	string	`"2024-09-16"`	Date when pregnancy reaches full term status
`disclaimer`	string	`"This is an estimate only. Due dates can vary. Consult your healthcare provider for medical advice."`	Medical disclaimer about estimated due dates

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Header	What it carries
`x-api-remaining-credits`	Credits left in the current cycle
`x-api-credits-used`	Credits spent in the current cycle
`x-api-max-credits`	The allowance for the cycle
`x-api-version`	Version of the endpoint that answered

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

Status	Meaning	What to do
`400`	Input was rejected	Read `error`; it names the parameter that has to change.
`401`	Key missing or invalid	Check the header name and the key value.
`403`	Key valid, but not permitted here	A key restriction or an IP allow-list — never a bad key.
`429`	Rate limited, or out of credits	Read `error` to tell them apart, then back off or top up.

What a call costs — 2 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Plan	Per month	Credits	Due Date Calculator calls	Per 1,000 calls
Free	Free	200	100	Free
Starter	$29.99	200,000	100,000	$0.30
Pro	$99.99	1,000,000	500,000	$0.20
Mega	$299.99	4,000,000	2,000,000	$0.15

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Compare all pricing tiers →

Call it from cURL — GET /v1/duedatecalculator

No SDK to install — this is a plain HTTPS call to /v1/duedatecalculator with your key in the x-api-key header. Swap in a real key and it runs as-is.

cURL

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curl "https://api.apiverve.com/v1/duedatecalculator" \
  -H "x-api-key: YOUR_API_KEY"

Resources

GitHubapiverve/duedatecalculator-apiSource, issues and the examples this page is built from.ReferenceDue Date Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/duedatecalculatornpm APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Node.js — GET /v1/duedatecalculator

Install the Node.js SDK, then call the Due Date Calculator API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — npm

npm install @apiverve/duedatecalculator

Node.js

const res = await fetch("https://api.apiverve.com/v1/duedatecalculator", {
  headers: { "x-api-key": "YOUR_API_KEY" },
});
const { data } = await res.json();
console.log(data);

Resources

npm@apiverve/duedatecalculatorThe published Node.js client, versioned and signed.GitHubapiverve/duedatecalculator-apiSource, issues and the examples this page is built from.ReferenceDue Date Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Python — GET /v1/duedatecalculator

No SDK to install — this is a plain HTTPS call to /v1/duedatecalculator with your key in the x-api-key header. Swap in a real key and it runs as-is.

Python

import requests

res = requests.get(
    "https://api.apiverve.com/v1/duedatecalculator",
    headers={"x-api-key": "YOUR_API_KEY"},
)
print(res.json()["data"])

Resources

Also published for

@apiverve/duedatecalculatornpm APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from C# / .NET — GET /v1/duedatecalculator

Install the C# / .NET SDK, then call the Due Date Calculator API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — NuGet

dotnet add package APIVerve.API.DueDateCalculator

C# / .NET

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("x-api-key", "YOUR_API_KEY");

var json = await client.GetStringAsync("https://api.apiverve.com/v1/duedatecalculator");
Console.WriteLine(json);

Resources

NuGetAPIVerve.API.DueDateCalculatorThe published C# / .NET client, versioned and signed.GitHubapiverve/duedatecalculator-apiSource, issues and the examples this page is built from.ReferenceDue Date Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/duedatecalculatornpm

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Go — GET /v1/duedatecalculator

No SDK to install — this is a plain HTTPS call to /v1/duedatecalculator with your key in the x-api-key header. Swap in a real key and it runs as-is.

req, _ := http.NewRequest("GET", "https://api.apiverve.com/v1/duedatecalculator", nil)
req.Header.Set("x-api-key", "YOUR_API_KEY")

res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))

Resources

Also published for

@apiverve/duedatecalculatornpm APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from PHP — GET /v1/duedatecalculator

No SDK to install — this is a plain HTTPS call to /v1/duedatecalculator with your key in the x-api-key header. Swap in a real key and it runs as-is.

PHP

$ch = curl_init("https://api.apiverve.com/v1/duedatecalculator");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-api-key: YOUR_API_KEY"]);

$response = curl_exec($ch);
echo $response;

Resources

Also published for

@apiverve/duedatecalculatornpm APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Ruby — GET /v1/duedatecalculator

No SDK to install — this is a plain HTTPS call to /v1/duedatecalculator with your key in the x-api-key header. Swap in a real key and it runs as-is.

Ruby

require "net/http"

uri = URI("https://api.apiverve.com/v1/duedatecalculator")
req = Net::HTTP::Get.new(uri)
req["x-api-key"] = "YOUR_API_KEY"

res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

Resources

Also published for

@apiverve/duedatecalculatornpm APIVerve.API.DueDateCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

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Due Date Calculator API

Try it — live request, no key required

About the Due Date Calculator API

What people use it for

Ways to call it

Other ways to use Due Date Calculator

Questions.

Request parameters — GET /v1/duedatecalculator

Required

Authentication

Response — GET /v1/duedatecalculator

Response fields

Response headers

Errors

What a call costs — 2 credits per call

Call it from cURL — GET /v1/duedatecalculator

Resources

Also published for

Call it from Node.js — GET /v1/duedatecalculator

Resources

Also published for

Call it from Python — GET /v1/duedatecalculator

Resources

Also published for

Call it from C# / .NET — GET /v1/duedatecalculator

Resources

Also published for

Call it from Go — GET /v1/duedatecalculator

Resources

Also published for

Call it from PHP — GET /v1/duedatecalculator

Resources

Also published for

Call it from Ruby — GET /v1/duedatecalculator

Resources

Also published for

Zero-code embed — one snippet, no backend

Changelog — Due Date Calculator API

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