Amazon says Kindle Fire makes up 22% of U.S. tablet sales

Amazon(s AMZN) announced this morning that the Kindle Fire is sold out, bringing the probability that the company will announce a new tablet at next week’s LA press event to roughly 1,000 percent. More surprising is Amazon’s claim that “in just nine months, Kindle Fire has captured 22 percent of tablet sales in the U.S.”

Amazon has never released an actual Kindle Fire sales number, so the 22 percent figure constitutes an unusual disclosure for the company. Even so, we don’t know how large Amazon thinks the entire U.S. tablet market is. I asked the company but don’t expect to get a number in response. Mashable suggests Amazon is going by this recent estimate from consulting firm Frank N. Magid.

Research firm IHS iSuppli says Apple’s (s aapl) iPad makes up 70 percent of tablet shipments worldwide — with Kindle Fire accounting for just 4.2 percent of global tablet shipments in Q2 2012. Since the Kindle Fire is sold only in the United States, though, its market share here is higher. Assuming that the iPad makes up at least 50 percent of U.S. tablet sales — a recent report estimated Apple at 55 percent and Android at 35 percent, though that was before the very successful launch of the iPad 3 — a 22 percent market share for Kindle Fire isn’t outrageous, though IHS’s data showed that Kindle Fire’s worldwide market share is falling.

So how many Kindle Fires have actually been sold? Using figures from the Apple-Samsung lawsuit to estimate the size of the rest of the U.S. tablet market, Publishers Marketplace estimates that Amazon sold 6.1 million Kindle Fires over nine months. That’s far below early analyst estimates, which had suggested Amazon would sell 6 million Kindle Fires in a single quarter — and with new competitors like the $199 Google (s GOOG) Nexus 7, the pressure is on for Amazon to announce something impressive at its event next week.