Portion Size Calculator

Turn a daily calorie target into real portions on the plate — grams of protein, carbs, vegetables and fat per meal — or scale any food from its nutrition label to the exact amount on your scale. Everything runs in your browser and every rate is editable.

📖 How it works & FAQ

What do you want to do?

Daily calorie target

Meals per day

Protein % of calories

Carbs % of calories

Vegetables % of calories

Fat % of calories

Protein kcal per gram (cooked lean)

Carbs kcal per gram (cooked)

Vegetables kcal per gram

Fat kcal per gram (oil, nuts)

How this portion size calculator works

The planner mode is a plate-method calculator with numbers attached. You give it a daily calorie target, and it divides those calories across four plate categories — protein, carbs, vegetables and fat — using percentages you can edit. Each category is then converted from calories into grams of actual food using a typical calorie density: cooked lean protein at about 1.5 kcal per gram, cooked carbs like rice or pasta at about 1.3, non-starchy vegetables at about 0.35, and fats such as oil or nuts at about 8. Divide by your meals per day and you get a per-meal portion in grams and ounces. If your percentages do not add to 100, the tool scales them so the plate always balances. The label mode is simpler: enter a food's serving size and its per-serving calories, protein, carbs and fat, then type the amount actually on your scale, and it multiplies everything by that ratio.

These figures are estimates only, not medical or nutrition advice; calorie needs and food densities vary, so check labels and talk to a professional for personal guidance.

How to use it

Choose a mode: plan portions from a calorie target, or scale a food from its label.
In planner mode, enter your daily calories and meals per day, then adjust the four percentages and calorie-per-gram values to match how you actually eat.
In label mode, copy the serving size and nutrition numbers from the package, then enter your real amount in grams.
Read the live results — every change updates instantly, and nothing leaves your browser.

FAQ

Why grams instead of cups or "palm-sized" portions?: Grams are unambiguous and match a kitchen scale. The ounce conversion is shown too, and hand-based guides are fine once you have calibrated them here.
What percentages should I start with?: The defaults — 30% protein, 40% carbs, 10% vegetables, 20% fat — are a common balanced starting point. Higher-protein or lower-carb plans just mean shifting the sliders.
Are the calories-per-gram values fixed?: No, all four are editable. Lean fish is lighter than fatty beef, and quinoa differs from bread, so tune them to your usual foods.
Is my data stored anywhere?: No. Everything is calculated in your browser and forgotten when you close the page.