Compare your dish to a similar recipe that already has nutrition data listed. Make sure you look at the recipe's serving sizes to ensure you are consuming what you expect to. Keep in mind that this will just give you a ballpark figure if the recipes are not an exact match
Try an online nutrient analysis tool (see Resources). Plug in your ingredients to find out what you are getting out of your meal. Many of these sites also feature calorie counters for recipes.
Calculate on your own. Look up each food you are using in the recipe. Add everything you are putting into the dish together, and then divide it by the number of portions you dish out. The U.S. Department of Agriculture's Web site has an excellent database you can use (see Resources).
Learn about portion sizes. Some things expand when cooked, such as pasta. If you do not plug in the correct portions, your calculations will be off.
Read nutrition labels (see Resources). If an ingredient comes in a package with a label, it will have the nutrient information listed. Make sure you know how many servings are in your package so your calculations are accurate.
Look up information in a nutrition textbook or dictionary. These texts can be a handy reference in your kitchen.