You can't weigh anything in a restaurant and you never will. So this is rough rules that hold up, not precision you can't have.
Sauces and dressings on the side. The least conspicuous thing you can ask for, nobody comments, and it's often 200 to 300 calories. Dip rather than drown and you'll use about a third.
Tomato-based sauces over cream. Grilled meat or fish with vegetables is the lightest thing on most menus. Pizza is more forgiving than people assume — it's the garlic bread and the second glass of wine doing the damage. A whole large pizza is 2,000+; half of one isn't.
Tandoori and tikka dishes are grilled and genuinely light. Avoid korma, passanda and anything described as creamy — often 800 to 1,000 on their own. Plain rice over pilau, one naan between two, and the poppadoms count.
Steamed over fried, every time. Chow mein beats sweet and sour, which is essentially battered meat in sugar. Boiled rice instead of egg fried saves 300 without changing the meal.
The hardest, because almost everything is fried. Steak, grilled chicken or a roast are the sane choices. Burgers are fine without the chips — it's usually the chips.
Fajitas, grilled, sour cream on the side. Burritos are enormous, often 1,200+, and nachos with cheese are a meal before your meal.
None of the above matters as much as having accounted for the meal in advance. Take 200 off the few days before and a restaurant stops being something you have to be good at.
Leeway is a free tool that does this arithmetic for you. Put what's coming up into the week and it spreads the cost across the days around it, with a floor it won't plan below.
Open the planner — freeLeeway is a planning tool, not medical or dietary advice. Calorie figures are typical estimates and vary by brand, measure and recipe. It isn't suitable if you have, or have had, an eating disorder or a disordered relationship with food. If you're unsure what a safe calorie target is for you, speak to a GP or registered dietitian first.