WASHINGTON — How strong is that pina colada? Depending on how it’s made, it could contain as much alcohol as two glasses of wine.

The National Institutes of Health is trying to spread the word: Take a look at its online alcohol calculator to see how much you’re really drinking with those summer cocktails.

A “standard drink” is the amount of alcohol in a 12-ounce beer, 5 ounces of wine or 1.5 ounces of distilled spirits. It’s a useful way to track alcohol consumption. But the multiple ingredients of mixed drinks make for a harder count.

“Most people don’t realize how much alcohol is actually in a drink,” said Dr. George Koob, director of the NIH’s National Institute on Alcohol Abuse and Alcoholism.

“Obviously it depends on the bartender and who’s mixing the drinks,” Koob adds. Recipes matter: The calculator’s pina colada example, for instance, assumes it contains 3 ounces of rum. Plan on using 2 ounces instead? The calculator adjusts to show it’s like 1.3 standard drinks.

What about a margarita? The calculator concludes it’s the equivalent of 1.7 standard drinks, if made with 1.5 ounces of tequila, an ounce of orange liqueur and half an ounce of lime juice.

A mojito? 1.3 standard drinks. A martini, extra dry? 1.4 standard drinks.

Other favorites? Type them in: http://rethinkingdrinking.niaaa.nih.gov/ToolsResources/CocktailCalculator.asp .

Also remember heat increases thirst but alcohol is a diuretic, Koob notes. So in addition to the usual advice to pace yourself — no more than one standard drink an hour — Koob says to stay hydrated by alternating some water or club soda with the alcohol.