Vocabulary words to goal
Language learners, teachers, and product teams that ship spaced-repetition apps all face the same planning question: if you already know a few thousand words, how many more must you learn before you hit a published milestone such as five thousand, eight thousand, or ten thousand headwords.
Run — free
Guessing from a deck size or a CEFR brochure is noisy; a clear gap number turns a vague ambition into a countable study plan. This vocabulary words to goal calculator accepts your current known word count and a non-negative target size, subtracts them with a floor at zero so overshoot never invents a negative debt, and returns words still to learn together with a progress ratio and percent you can pin on a dashboard. The same pure parse logic powers the free browser widget and the prepaid API path, so homework checks, LMS plugins, and edge workers never disagree on the arithmetic. Failed validation is not billed; successful calls use the published $0.002 base price with no model tokens and no outbound network.
How to use it
Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.
Check your inputs
Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.
Use it again or automate it
Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.
What you can do with it
Get an answer now
Enter one set of values and see the result without building a spreadsheet or script.
Compare scenarios
Change one value at a time and rerun the calculation to understand what affects the result.
Automate repeated work
Use the API when the same calculation needs to run inside your product or workflow.
FAQ
How do I use this capability?
Complete the fields above and run it on this page. The form highlights anything that needs attention.
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/edu/vocab-words-to-goal \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"known":2500,"target":5000}'const res = await fetch("https://api.kit.forhosting.com/edu/vocab-words-to-goal", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"known": 2500,
"target": 5000
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/edu/vocab-words-to-goal",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"known": 2500,
"target": 5000
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/edu/vocab-words-to-goal", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"known":2500,"target":5000}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"known":2500,"target":5000}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/edu/vocab-words-to-goal", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"known": 2500,
"target": 5000
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "edu.vocab_words_to_goal",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |