Whenever possible, weighing your food is the most accurate way to log it. But there will be times — restaurants, vacations, parties or meals at someone else’s house — when you simply can’t put your food on a scale.

Don’t let the inability to be exact become a reason not to log it. A reasonable estimate is much more useful than no entry at all.

When you need to estimate:

If the restaurant publishes nutrition information, use the restaurant’s own entry in MyFitnessPal when available. Keep in mind that actual portions can vary from the published serving, so if your portion appears noticeably larger or smaller, adjust your entry accordingly.

If you’re eating at a restaurant without nutrition information, search MyFitnessPal for a similar dish. Compare several reasonable entries rather than automatically choosing the lowest-calorie option. Consider the ingredients, portion size, sauces, oils and preparation when deciding which entry seems most realistic.

You can also “deconstruct” the meal. For example, at a taco bar you might separately estimate and log the tortillas, meat, cheese, sour cream and other toppings. This can often produce a better estimate than searching for a generic “taco.”

When portions are uncertain, it’s reasonable to estimate somewhat conservatively rather than assuming the smallest possible amount. Restaurant foods in particular may contain more oil, butter, sauces or other calorie-dense ingredients than you would use preparing the same meal at home.

Most importantly, don’t chase false precision. There’s no way to know whether an unweighed restaurant meal contained exactly 742 calories. Make your best reasonable estimate, log it, and move on.

Occasional estimates won’t ruin your progress. If you’re estimating most of your meals, however, it becomes much harder for you and your coach to know how closely you’re actually following your prescription.

Be as accurate as reasonably possible when you can, make your best estimate when you can’t, and always log it.