Card Centering Checker
Measure the centering of Pokémon, One Piece and other TCG cards from a photo — left/right and top/bottom ratios, right in your browser.
The Card Centering Checker measures how evenly a trading card’s printed frame sits inside its borders — the left/right and top/bottom “centering” that collectors check before sending a card such as a Pokémon or One Piece card in for professional grading. Take or upload a photo, align four corners, and the tool straightens the image and measures the border on all four sides, reporting each pair as a ratio such as 55/45.
Works for Pokémon, One Piece and other trading cards. Processed 100% on your device — the photo is never uploaded.
Step 1 — drag the four corners onto the corners of your card, then measure.
Step 2 — the photo has been straightened. The coloured lines sit on the card's inner frame: drag any line if it looks off, the numbers update live.
Your photo is measured on this device only and discarded from memory when you reset or close the tab. Nothing is uploaded, stored or logged.
Next step: estimate whether grading is worth it → TCG Grade ROI calculator (SkillAisle)
How to use
- Add a photo of the card front — tap to take one, drop a file, or paste. Best results: card lying flat, shot straight-on in even light, filling most of the frame.
- Drag the four corner handles onto the exact corners of the card. The tool tries to find them automatically first; nudge any corner that is off, then press “Measure centering”.
- The photo is straightened (perspective-corrected) and the tool finds the card’s inner frame. Check the coloured guide lines — drag any line that is not sitting on the frame, and the ratios update live.
- Read the left/right and top/bottom ratios, then switch to “Card back” and repeat if you want the back measured too. Download a PNG summary or copy the text result — everything stays on your device.
About this tool
Everything runs locally in your browser with plain Canvas image processing — there is no server, no account and no upload. Your photo is held in the page’s memory only, and is discarded when you reset the tool or close the tab. That also means it works offline once the page has loaded.
The measurement is an estimate from a photograph, not an official measurement: camera angle, lens distortion, glare and worn or rounded card corners all nudge the numbers. It is designed as an honest pre-check — a quick way to spot a clearly off-center card — not as a verdict on any grade.
How it works
After you align the corners, the tool maps the card to a rectangle with a perspective (homography) transform, so a slightly tilted photo still measures as if the card had been scanned flat.
On the straightened image it reads the border colour from the very edge of the card, then scans inward from each side to find where that colour stops — that boundary is the card’s printed inner frame — and places four guide lines there. You can drag every line, so the final measurement is always the one you approved with your own eyes.
Each ratio compares the two opposite borders: left/right = left border ÷ (left + right border), expressed as a pair that adds to 100 (for example 55/45). The verdict text only describes how even the borders look — well centered, slightly, noticeably or well off-center — it never converts the numbers into a grade.
Frequently asked questions
Does this tool predict a PSA or CGC grade?
No. It reports a centering estimate from your photo, in plain ratios. Grades weigh corners, edges, surface and print quality as well as centering, and only the grading companies can assign them. This site is not affiliated with PSA, CGC or any grading company.
Is my card photo uploaded anywhere?
No. The photo is processed by JavaScript in your browser and never sent over the network — there is no upload endpoint for it to go to. You can check in your browser’s network inspector, or load the page, go offline, and measure anyway.
Which cards does it work with?
Any trading card with a visible border and inner frame: Pokémon, One Piece, Magic: The Gathering, Yu-Gi-Oh! and most sports cards. Borderless full-art prints have no inner frame to measure against, so the guide lines will need your eyes more than the auto-detect.
How accurate is the measurement?
With a flat, straight-on, glare-free photo and the corners and guide lines checked by eye, the ratios are typically within a couple of points of a careful ruler measurement on the physical card. A tilted or shadowed photo is the main source of error — retake rather than trust a bad shot.
Why measure the back as well?
Collectors and graders look at both sides, and a card can be well centered on the front and off on the back. The back tab measures the back photo independently, and the summary shows both results together.
What do the ratios mean — is 50/50 perfect?
50/50 means the opposite borders are exactly equal, which is perfectly centered. Real cards are printed and cut with small tolerances, so readings in the low-to-mid 50s are common even on cards that look straight. The further the bigger number climbs, the more visible the lean.
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