Convert images to PDF
A 2400 × 3000 scan at 300 DPI becomes a 576 × 720-point portrait page with a 4:5 ratio, while a 1920 × 1080 photo becomes a 16:9 landscape page. Plan every page of a photo book or mixed scan before building it. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Dpi
- 300
- Page count
- 3
Plan an image-based PDF before creating or uploading any files. Enter each image's pixel width and height in the intended order, choose the resolution in dots per inch, and receive the exact width and height of every resulting PDF page in points. The calculation keeps each source aspect ratio, identifies portrait, landscape, or square pages, and reports a simplified ratio when the dimensions are integers. It is useful for validating mixed scans, photo books, contact sheets, and automated document workflows without processing the image data itself.
Turn ordered image dimensions into a page plan
An image-to-PDF job often begins with a collection of scans or photographs that do not share one size. Before assembling the document, enter one width and height record for every image, keeping the records in the same order as the intended pages. The calculator returns one page record for each input record, numbered from one, so the result doubles as a compact page plan.
It does not reorder, crop, stretch, or inspect image files. That makes the calculation safe to use early in a workflow, including before the files have been transferred. Each result includes width and height in PDF points, the preserved aspect ratio, and an orientation label.
Mixed portrait and landscape sources remain mixed instead of being forced into a common paper format. A square image remains square. If the dimensions are positive integers, the ratio is reduced to a familiar form such as 4:5 or 16:9, making unexpected source dimensions easy to spot before PDF generation begins.
Understand pixels, DPI, and PDF points
Image dimensions are entered in pixels, while PDF page dimensions are expressed in points. A PDF point is a physical unit: seventy-two points equal one inch. The DPI setting tells the calculator how many image pixels should occupy one inch, so the conversion is width multiplied by 72 and divided by DPI, with the same operation applied to height.
Because both axes use the same scale factor, the source aspect ratio is preserved. For example, raising DPI produces a smaller physical page without changing its shape or discarding pixels. The default of 72 DPI maps one pixel to one point, which is convenient when dimensions already represent the desired coordinate size.
Use the actual placement resolution required by the downstream PDF generator when physical print size matters. The tool does not resample images or make claims about visual quality; it calculates geometry only.
Validate the result before building the PDF
Review the returned page count first; it must equal the number of image dimension records supplied. Then scan the orientation and aspect ratio fields for outliers. A landscape page inside a sequence of portrait scans may be intentional, but it can also reveal swapped width and height values.
Compare point sizes when preparing print, imposition, or viewer layouts, especially if images came from devices with different pixel dimensions. The calculation accepts fractional dimensions for analytical workflows, although ordinary raster images normally use integer pixels. Every width, height, and DPI value must be finite and greater than zero, and the ordered list must contain at least one image.
The output describes the natural page size at the chosen DPI; it does not add margins, bleed, rotation, or a standard-paper fitting step. If a later PDF builder adds any of those transformations, apply them after this baseline calculation and document that change separately.
What you can do with it
Preflight a scan bundle
Find rotated or unusually sized pages from dimension metadata before combining confidential scans into a document.
Plan a photo PDF
Calculate the natural physical page size of each ordered photograph at the resolution selected for export.
Validate an automated pipeline
Compare a PDF generator's emitted page boxes with a deterministic page plan produced from the same image manifest.
FAQ
Does this tool create or download a PDF?
No. It calculates the ordered page geometry that an image-to-PDF process should produce; it does not receive image files or create a binary document.
How is each PDF page size calculated?
Each pixel dimension is multiplied by 72 and divided by the selected DPI. The same scale is applied to width and height, so the aspect ratio remains unchanged.
Can pages have different sizes and orientations?
Yes. Every image produces its own page dimensions, and portrait, landscape, and square pages can appear together in any order.
Does changing DPI alter the aspect ratio?
No. DPI changes both page dimensions by the same factor, affecting physical size but not shape.
Which DPI value should I choose?
Use the placement resolution your PDF generator will actually apply when physical print size matters. The default of 72 maps one pixel to one point; a higher value gives a smaller page with exactly the same shape.
Related tools
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/pdf/images-to-pdf \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"images":[{"width":2400,"height":3000},{"width":1920,"height":1080}]}'const res = await fetch("https://api.kit.forhosting.com/pdf/images-to-pdf", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"images": [
{
"width": 2400,
"height": 3000
},
{
"width": 1920,
"height": 1080
}
]
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/pdf/images-to-pdf",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"images": [
{
"width": 2400,
"height": 3000
},
{
"width": 1920,
"height": 1080
}
]
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/pdf/images-to-pdf", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"images":[{"width":2400,"height":3000},{"width":1920,"height":1080}]}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"images":[{"width":2400,"height":3000},{"width":1920,"height":1080}]}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/pdf/images-to-pdf", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"images": [
{
"width": 2400,
"height": 3000
},
{
"width": 1920,
"height": 1080
}
]
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "pdf.images_to_pdf",
"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.
Limits
max_items | 1000 |
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. |
Technical notes
Validate the result before building the PDF
A request may include no more than one thousand records, keeping browser and API execution bounded.
Technical questions
What happens if the image list is empty?
The request fails with an invalid input error because a PDF page plan requires at least one image dimension record.
What does the API request cost?
The API costs $0.002 per request. The same deterministic calculation can also run free in the browser.