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IMO number checker

Type a ship's seven-digit IMO number. Voydar checks the check digit and, when the number is well formed, shows the ship that holds it.

Try: 9074729, 9321483

Check digit passes

IMO 9321483 is a well-formed IMO number.

Voydar's register lists this number for EMMA MAERSK.

Follow this vesselOpens its page; sign in to get an alert when it arrives, leaves or changes destination.

How the check digit works

An IMO number is six digits and a seventh check digit. Multiply the first six digits by 7, 6, 5, 4, 3 and 2, add the products, and the last digit of the sum must equal the seventh digit.

9074729: 9x7 + 0x6 + 7x5 + 4x4 + 7x3 + 2x2 = 139, last digit 9, check digit 9.

The scheme is IMO resolution A.600(15). It catches most single typing errors and most swapped neighbouring digits.

What this check cannot tell you

  • A passing number is not proof that a ship holds it: many valid numbers were never assigned.
  • An IMO number belongs to the hull for life, but a name, flag and owner change; the ship page shows the latest Voydar holds.
  • An IMO number is not an MMSI: the MMSI is nine digits and belongs to the radio. The guide on IMO against MMSI explains the difference.

Information only — not for navigation. Never use these results to plan or conduct a passage.

How this works

  1. The number is cleaned (an optional IMO prefix, spaces and hyphens removed) and must be seven digits.
  2. The check digit is computed from the first six digits with the weights 7 to 2 (IMO A.600(15)) and compared with the seventh.
  3. A well-formed number is looked up in Voydar's ship register by IMO; only the name and the link to the ship page are shown here.