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
No key required to try it. Get a key to use it in your app.
{
"status": "ok",
"error": null,
"data": {
// Due Date Calculator response payload
}
}
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
Other ways to use Due Date Calculator
Same data, same APIVerve account, same credit balance — one key works on all of them.
What does the Due Date Calculator API do?
How do I authenticate Due Date Calculator API requests?
How much does the Due Date Calculator API cost?
How fast is the Due Date Calculator API?
What response formats does the Due Date Calculator API support?
What HTTP method does the Due Date Calculator API use?
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_periodRequired | string | 2025-06-01 | First day of last menstrual period (YYYY-MM-DD) date |
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-keyRequired | Every request | Your API key. Header names are case-insensitive, so X-API-Key is the same header. |
AuthorizationAlternate | Instead of the above | Bearer <key> — for clients that only expose bearer auth. Resolves to the same account and the same billing. |
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.
{
"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_datePremium | string | "2024-01-01" | First day of last menstrual period in ISO format |
estimated_conception_datePremium | 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_pregnantPremium | number | 715 | Total number of days pregnant |
weeks_pregnantPremium | number | 102 | Number of complete weeks of pregnancy |
days_into_weekPremium | number | 1 | Additional days beyond complete weeks |
formattedPremium | string | "102 weeks, 1 days" | Human-readable pregnancy duration with weeks and days |
trimesterPremium | number | 3 | Current trimester number: 1, 2, or 3 |
percentage_completePremium | number | 255.36 | Pregnancy completion percentage relative to due date |
time_until_due | object | {...} | How long until the due date, with a formatted summary |
daysPremium | number | 0 | Complete days remaining until due date |
weeksPremium | number | 0 | Complete weeks remaining until due date |
days_extraPremium | number | 0 | Additional days beyond complete weeks remaining |
formattedPremium | string | "Past due date" | Human-readable time remaining until delivery |
is_overduePremium | boolean | true | Whether pregnancy has passed the due date |
upcoming_milestonesPremium | array | [] | Array of upcoming pregnancy milestones and dates |
important_dates | object | {...} | Key milestones: the end of each trimester and viability |
end_first_trimesterPremium | string | "2024-04-01" | Estimated end date of first trimester |
end_second_trimesterPremium | string | "2024-07-08" | Estimated end date of second trimester |
full_term_beginsPremium | 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.
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 "https://api.apiverve.com/v1/duedatecalculator" \
-H "x-api-key: YOUR_API_KEY"Resources
Also published for
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.
npm install @apiverve/duedatecalculatorconst 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
Also published for
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.
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
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.
dotnet add package APIVerve.API.DueDateCalculatorusing 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
Also published for
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
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.
$ch = curl_init("https://api.apiverve.com/v1/duedatecalculator");
curl_setopt($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
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.
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.bodyResources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Zero-code embed — one snippet, no backend
Drop an interactive Due Date Calculator form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.
Changelog — Due Date Calculator API
Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.
Entries are picked up from dated catalog snapshots, so the first one appears after the next snapshot that moves something. A period where nothing changed produces no entry — silence is a valid changelog for the Due Date Calculator API.
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