Ryanair are very strict,be careful as it will end up costing you ! Cabin baggage size is standard with all airlines 55x40x20 so that it can fit into the overhead lockers. However Ryanair are particularly strict on the baggage weight max 10kg. Sounds like you've bought a standard sized bag.
Will away bigger carry-on fit on Ryanair?
While we're certain our Bigger Carry-On won't fit, we've had customers successfully take the Carry-On onto Ryanair flights. We can't guarantee this as boarding is truly a case-by-case situation!