Serving size calculator
This serving size calculator handles three everyday tasks: estimating food quantity for guests, finding full servings in a prepared batch and dividing total dish calories among servings.
Choose one quantity unit for the calculation. You can work in grams, kilograms, millilitres, litres, ounces or items without rounding intermediate values.
Amount to prepare
3,300 g
Before allowance
3,000 g
Formula
guests × serving size × (1 + allowance ÷ 100)
Current-value substitution
12 × 250 × (1 + 10 ÷ 100) = 3,300 g
Three calculation modes
- Food for guests: guests × serving size × (1 + extra allowance ÷ 100).
- Servings from a batch: total quantity ÷ serving size.
- Calories per serving: calories in the whole dish ÷ actual number of servings.
- The batch mode reports both full servings and the remaining quantity.
Example: food for 12 guests
At 250 g per person, the base amount is 12 × 250 = 3,000 g. A 10% allowance adds 300 g, so the amount to prepare is 3,300 g, or 3.3 kg.
An allowance is useful for a buffet where guests serve themselves. For plated meals, use 0% when the guest count and serving size are already fixed.
Adult serving-size starting points
Portion size depends on the menu, event length and guests. These ranges are planning starting points, not dietary requirements.
| Food | Starting amount per person |
|---|---|
| Main dish | 180–250 g |
| Side dish | 150–200 g |
| Salad | 100–150 g |
| Appetisers in total | 150–250 g |
| Dessert | 100–150 g |
Recipe servings and calories
To find the number of servings, weigh the finished food without its container and divide by the chosen serving size. A 2,850 g batch at 250 g per serving makes 11 full servings with 100 g left over.
Calories per serving use only the total you enter; the calculator does not analyse ingredients. If a whole dish contains 2,400 kcal and is split into 8 equal portions, each portion contains 300 kcal.
Frequently asked questions
How do I calculate food quantity for guests?
Multiply the guest count by the serving size, then add your chosen allowance. Twelve people at 250 g each with 10% extra require 3,300 g.
How do I find servings in a prepared dish?
Divide the finished weight or volume by one serving size. The calculator also reports any amount left after the last full serving.
How do I calculate calories per serving?
Divide the calories in the complete prepared dish by the number of equal servings. Portions should be roughly equal in weight.
How much extra food should I allow?
Five to ten percent is often enough for a known guest count. A buffet, longer event or uncertain attendance may justify a larger allowance.
Can I scale every recipe ingredient here?
Use the recipe scaling calculator for that task. It multiplies each ingredient by the ratio of the new serving count to the original count.
Updated: 2026-08-16