Quick answer
Portion per person = total amount ÷ number of people. 3 kg of food for 10 people is 0.3 kg each, or 10% of the total per person.
Enter the total amount of food and the number of people. The calculator returns the amount per person and the share. Use this portion size calculator to check your own figures.
Related tools: Food Waste Percentage Calculator: Share of food that was wasted. Course Credit Calculator: Terms left to graduate from credits needed and taken per term. Sample Size Calculator: Sample size for estimating a mean or a proportion.
How to use the Portion Size Calculator
- Enter total amount of food (above 0).
- Enter people (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Total amount of food | A number | > 0 |
| People | A number | > 0 |
Formula and method
Formula
per person = total ÷ people
IEEE-754 double precision; shown to the decimals indicated.
Use any unit; the answer is in the same unit.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Total amount of food = 3; People = 10.
| Result | Value |
|---|---|
| Per person | 0.3 |
| Per person in % | 10% |
Example 2
Inputs: Total amount of food = 5.5; People = 12.
| Result | Value |
|---|---|
| Per person | 0.458 |
| Per person in % | 8.33% |
The first line is the headline result (per person). Below it the portion Size Calculator lists per person in %, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Planning quantities
Typical main-course portions are about 150 to 250 g of meat, 150 g of cooked rice or pasta and 100 to 150 g of vegetables per person. Buffet-style meals use smaller portions per dish, since guests take several.
Working backwards
To decide how much to buy, multiply the portion by the guests and add 10% for seconds. Entering your cooked total reveals if the portions are generous or tight.
How the result changes with total amount of food
Holding every other input at the first worked example, this table changes only total amount of food. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Total amount of food | Per person | Per person in % |
|---|---|---|
| 1.5 | 0.15 | 10% |
| 3 | 0.3 | 10% |
| 6 | 0.6 | 10% |
| 12 | 1.2 | 10% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Total amount of food: entering "0" shows "Total amount of food must be greater than 0." beside that field and no result.
- People: entering "0" shows "People must be greater than 0." beside that field and no result.
Choosing between the Portion Size Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Food Waste Percentage Calculator](/cooking/food-waste-percentage-calculator/) | food wasted and total food | Food waste |
| [Course Credit Calculator](/education/course-credit-calculator/) | credits needed to graduate, credits completed and credits per term | Terms remaining |
| [Sample Size Calculator](/statistics/sample-size-calculator/) | estimate a, confidence level and margin of error | Required sample size |
| [Budget Calculator](/finance/budget-calculator/) | monthly income, housing and food | Left over each month |
| [College Cost Calculator](/finance/college-cost-calculator/) | annual cost today, years until study starts and annual cost increase | Projected total cost |
Background: cooking measurements
For baking, weight is more reliable than volume. A cup holds a fixed volume but its weight depends on the ingredient's density, and a cup of flour can vary by 20 to 30 grams depending on how it is scooped, so published gram-per-cup values for the same ingredient differ from site to site. Spoon and level flour if you must measure by volume.
Check which cup a recipe uses: the US cup is 236.588 mL, while a metric cup is 250 mL.
Assumptions and limitations
- Guests must be positive
Cooking times are guides. Use a food thermometer to confirm safe internal temperatures.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for total amount of food and people to confirm this.
Frequently asked questions
How much meat per person?
About 150 to 250 g cooked.
Should I plan for seconds?
Allow roughly 10% extra for second helpings when several dishes are served, and more if the dish is the only main.
Does the unit matter?
Use the same unit for the output.
What does the Portion Size Calculator calculate?
Amount of food per person. It returns Per person and Per person in %.
What formula does the Portion Size Calculator use?
per person = total ÷ people. Use any unit; the answer is in the same unit.
What do I need to enter in the portion Size Calculator?
You enter Total amount of food and People.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Guests must be positive.
What is an example of a portion Size result?
With total amount of food 3 and people 10, the per person is 0.3.
Can I rely on this calculator for a decision?
Cooking times are guides. Use a food thermometer to confirm safe internal temperatures. For this calculator in particular: Guests must be positive.
Related calculators
- Food Waste Percentage Calculator — Share of food that was wasted.
- Course Credit Calculator — Terms left to graduate from credits needed and taken per term.
- Sample Size Calculator — Sample size for estimating a mean or a proportion.
- Budget Calculator — Monthly income minus spending, and the share left over.
- College Cost Calculator — Projected total cost of study with yearly cost inflation.
- Net Worth Calculator — Total assets minus total liabilities.
- Event Capacity Calculator — Guests that fit in a space at a space-per-person allowance you choose.
Sources
- OpenStax, Prealgebra 2e (Rice University): fractions, decimals, percents, ratios and rounding
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B conversion factors (international inch 25.4 mm, avoirdupois pound 0.45359237 kg)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.