The smart container number checker.
A container number is valid when its last digit, the check digit, matches the one calculated from the first ten characters: the 3-letter owner code, the equipment category letter and the 6-digit serial. That rule comes from ISO 6346, whose owner-code register is kept by BIC. Type the number below for an instant verdict. If it fails, the checker tests one-character misreads (O↔0, I↔1, B↔8) and shows the likely intended number. A pass means the number is consistent, not that the container is registered or in your yard. Runs in your browser, no signup, no upload.
Why does a scanned container number fail validation?
Most failures are not bad containers, they are misread characters. O read as 0, I as 1, B as 8, S as 5, and Z as 2 are the common ones, and any single swap breaks the ISO 6346 check digit. This checker runs the math, then tests one-character corrections at the positions where each confusion is possible and reports the likely intended number.
Why a checker that fixes, not just flags.
A container number is four letters and seven digits, and that final digit is a modulo-11 check digit computed from the first ten characters. When a scanner misreads a single character — a faded 0 read as O, a rusted 8 read as B — the check digit no longer matches and the number is rejected. A plain validator stops there. In a real yard, that means a clerk re-typing under pressure, or a wrong number slipping into the gate log.
Step 1 — Validate
The eleventh digit is recomputed from the first ten characters using the ISO 6346 modulo-11 formula and compared to what you typed. Match means the number is internally consistent.
Step 2 — Auto-correct
If it fails, the checker tries a single-character repair on the confusables OCR mistakes most — O↔0, I↔1, B↔8, S↔5, G↔6, Z↔2, A↔4 — keeping the first four positions letters and the last seven digits, then re-validates. One clean candidate is shown as the likely correct number.
The same check runs inside the Vantage app.
The auto-correct above is one taste of what Vantage does automatically. In the iPhone app, Vantage reads trailer and container numbers from a photo; container numbers also get the ISO 6346 check digit and a one-character repair when only one fix passes it; the clerk confirms every read.
Photo, not typing.
A clerk photographs the number from a phone. Works offline in the iPhone app, no kiosks, no fixed cameras at the gate.
Checked before it lands.
Container reads are checked against the ISO 6346 check digit and single-character misreads are auto-corrected; the clerk confirms every read before it is saved.
Fewer typos in the gate log.
The clerk checks each read at the gate, not three hours later in the yard.
Run the whole pipeline on a phone.
Vantage YMS — free plan with no card, paid plans from $149/mo, no setup fee.
Frequently asked
Does this fix OCR misreads in a container number?
Yes. If a number fails the ISO 6346 check digit, the checker tries a single-character repair on the visual confusions OCR makes most — O↔0, I↔1, B↔8, S↔5, G↔6, Z↔2, A↔4 — keeping the first four positions letters and the last seven digits, then re-validates. If exactly one corrected candidate passes the check digit, it's shown as the likely correct number. The Vantage iPhone app runs the same check on every container number it reads from a photo.
Does it run in my browser?
Yes. The checker runs entirely in your browser in JavaScript. Nothing is uploaded, logged, or stored — you can disconnect your network and it will still validate and auto-correct.
A valid check digit means the container is real, right?
Not necessarily. A valid check digit confirms the number is internally consistent, not that it belongs to a real, registered container. Vantage YMS pairs this with your appointment data so a valid-but-unexpected container gets flagged at the gate, not after the fact.
Does this work for trailer numbers and US domestic intermodal?
This checker covers ISO 6346 sea/ocean containers (four letters, seven digits). Vantage YMS itself reads container numbers, trailer numbers, license plates, and chassis numbers — but that's a job for the app, not this tool. Just need the check digit on a clean number? Use the basic calculator.
The other free tools
Put this checker on your own site
Free to embed on any site, no permission or attribution needed beyond the small credit line inside the widget. It loads a stripped-down view with no header, no footer, and no marketing.
Stop re-typing misread numbers.
Vantage YMS — free plan with no card, paid plans from $149/mo. Cancel anytime.