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Centering, and only centering. It photographs the card, corrects the photograph for perspective, and measures the printed border on all four sides in millimetres — front and back — to give left/right and top/bottom ratios. Those ratios are compared against the centering tolerances PSA, Beckett (BGS) and CGC each publish, and the app reports the highest grade each house's published centering rule would allow.

Because it cannot know one. Centering is the only criterion any grading house publishes numeric tolerances for, so it is the only one that can be measured. What Gemcheck reports is a ceiling— the best a card could do on centering alone. Corners, edges and surface can cap the real grade far lower, and PSA explicitly reserves a variance at the grader's discretion. Reporting a centering ceiling as though it were a grade is the most common way automated card grading goes wrong, and this app refuses to do it.

No. No grading house publishes numeric criteria for them, and Gemcheck does not invent any. It magnifies each corner and each edge strip so you can look at them yourself, ranks the four corners against each other, and teaches the two heuristics that matter most — printed white that follows the design is not whitening, and a cut-edge bevel catches light as a thin uniform line while wear is irregular. None of that is turned into a subgrade or folded into the reported figure.

Two photographs of the same card, at slightly different angles, share no error sources except the card itself. Gemcheck measures both independently; if they disagree by more than 1.5 points, one of the rectifications is wrong and the app asks you to re-shoot rather than quoting a figure it does not trust. The same applies when the border detector cannot find a reliable transition — for example on a borderless full-art front, where you are asked to place the reference yourself.

Borderless full-arts and alt-arts have no printed frame to detect automatically. They are not unmeasurable, just not automatable: in the adjust screen you place the reference lines yourself — the art edge, a framing element, or nothing at all — which is exactly what a human grader does with the same card. Every English Pokémon back is the same bordered design, so back centering is measurable on every card either way, and the app will report the back alone and say so if you decline.

On the adjust screen there are two independent layers. The four corner handles are the cut edge — moving them re-rectifies the photograph. The four dashed lines are the printed border, and they move independently of each other, because centering is four distances and a printed frame is not guaranteed square to the cut. A loupe follows your finger, offset so your fingertip never covers the line you are placing, the lines snap to the nearest strong edge, and the ratios update live. “Reset to auto” is always there.

No. Everything is measured on the device, and no photograph is transmitted. There is no account, no login, and no server of ours that your card images touch. There are no analytics, attribution or crash-reporting SDKs in the app at all. Full detail is in the Privacy Policy.

Free gives you 3 scans to try, with the full measurement and the full manual adjustment — nothing about the measurement is held back. They are a trial rather than a monthly allowance, so they do not come back. Gemcheck Pro removes the limit: $39.99 a year with a 1 week free trial, or $5.99 a month with no trial.

Subscriptions are billed by Apple, so they are cancelled through Apple: iOS Settings → your name → Subscriptions, or apps.apple.com/account/subscriptions. Cancelling stops the next renewal and you keep access until the period you have paid for ends. Refunds are also Apple's — request one at reportaproblem.apple.com. We cannot cancel or refund on your behalf. Deleting the app does not cancel a subscription.

Open Settings inside the app and tap Restore purchases. Because there is no account, entitlement is restored from your Apple Account rather than from anything we store.

No, and that is the trade-off for keeping your cards private. Your measurements and binder are stored only on your device, so deleting the app removes them and we hold no copy to restore.

No. Gemcheck is an independent tool and is not affiliated with, endorsed by or sponsored by PSA, Beckett/BGS, CGC or The Pokémon Company. The centering tolerances it compares against are taken from each company's own published standards and are named so you can see which rule produced which answer.

Email us using the button above. For a wrong measurement, the single most useful thing you can send is the photographs you took plus what the app reported and what you believe the correct figure is — measurement bugs are almost impossible to chase without the original pixels.