ISIS by the numbers: How big, strong and rich the militant organization may be

Trying to take an inventory ofISIS is a daunting task, even for those senior analysts in the intelligence community few rely on the annual statistical reports that the media-savvygroup actually releases.

But experts have been able to provide someestimates onhow big, how strong and how richthe militant organization may be.

"When you hear the intelligence community say they don't even know, that's somewhat worrisome," saidColin Clarke, an associate political scientist at the RandCorporation, whichspecializes in insurgency and transnational terrorism.

10,000 to 20,000: The number of fighters

Clarkepegged the ISIS fighting force at around 10,000, afar cry fromsome estimates that have placed that number as high as 80,000.

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"When people throw out these numbers, I'd ask them what do they define as a fighter," said Lauren Squires, a counter-terrorism analyst at the Institute for the Study of War.

We look at the battle-hardenedbattalionmanoeuvregroups. Wethinkof that as up to 20,000 [fighters]."

Austin Long, assistantprofessor of international and public affairs at Columbia University and a formeradviser to the multinational force in Iraq, said the number of "true believers" probably numbers in the low thousands. But thereare also those who are part of the fightingbecause they see ISISas "thewinningteam,"which he said couldput the force at around 15,000, although he says 20,000 is also possible.

$1Mto $4M: The amount of revenue ISIS takes in a day

Generating revenue is one of the organization's biggeststrengths and ithashistorically, been fantastic at generating revenue from a lot of different sources, Long said.

Unlikeal-Qaeda, which receivesmuch of its fundingfrom wealthy Gulf state patrons, ISIS self-generates much of its revenue, said Clarke. Carjackings, bank robberies,extortion, kidnappingsfor ransom are all used to fund its organization.

"The group is like the Mafia. It reallydoesntdiscriminatein how it gets its money," Clarke said. "Anythingthat's a revenue generatingactivity, this group isengagedin."

How much it has and how much it takes in is again difficult to discern. Some estimates believe ISIS takes in around $1 million a day, while others estimate around$25 million to $30 million a year.

Squires said their institute pegged it higher,at around $2 million to $4 million daily.

Regardless of the number, Clarke said ISISs financial resources go well beyond anything al-Qaeda had at itsapex with Osama bin Laden at the helm.

Acquiring territory, however, also comes with the expense of running the areas itcontrols.

"This isn't money that's justsittingin a piggy bank," Clarkesaid. "As the group grows its recruiting base, it has to pay these fighters. It has to pay for this. It's establishing a caliphate and running a caliphate is not cheap. There's moneygoingout, not just coming in."

3 divisions worth: ISIS's stockof weapons and equipment

"When you look at them as a conventional force, they have approximatelyat least three divisions if you think of a Western military division worth of equipment," Squires said.

"But these are only operable if ISIS is undergoing a conventional operation. Theyare more lethal and more productiveas a terrorist organization."

Its really less aboutquantitythan it isabout the quality of weapons, Clarke said. ISIS has raided a number of Iraqi military depots, acquiring all sorts of weapons, including sniper rifles, mortars, heavy machine guns, anti-tank weapons, RPGs, tanks, and Humvees.

Most troubling, says Clarke, is ISISs recent grab of portableair defence systems calledMANPADs shoulder-mounted homing missiles that are relatively simpleto use and can reach aircraft flying as high as 5,000 metres.

90,000: The number ofsquare kilometres ISIS is believed to control

The amount of territory held by ISIS changesby the day, said Clarke but it includesbig swaths of north and northeast Syria to include major cities like Aleppo and Raqqa. ISIS also hasa major presence around acritical border crossing between Syria andIraq. In Iraq, ISIS's reach stretches to thenorthern and northwestern parts of country, but also goesas far down as Fallujah and west of Kirkuk.

The New Yorkerestimated that, in total, ISIS controls about 90,000 square kilometres of landabout the size of Jordan.