Full carry is the ceiling on how wide a contango can get in a storable commodity, because at that point cash-and-carry-arbitrage becomes profitable and sellers of the deferred contract flood in. Market commentary often quotes spreads as a percentage of full carry.
A market trading at 90-100% of full carry is signalling abundant supply and plenty of empty storage; nobody wants the commodity now and holders are being paid to store it. A market at 20% of full carry, or in backwardation, is signalling scarcity and a positive convenience-yield.
Example: corn at $4.50, financing 5.5% and commercial storage 4 cents a bushel a month means carry of about 6 cents a month. If the three-month spread is 12 cents against a full carry of 18 cents, the market is at 67% of full carry.
Related: cost-of-carry, cash-and-carry-arbitrage, contango, storage-cost, convenience-yield