Skip to content
Calcapedia
Menu
Health & Fitness

Baby Size Kitchen Staples Calculator

Compare a typical baby's weight at any week of pregnancy with eggs, butter, flour, sugar, pasta and milk.

Level: Grades 4–5

Printable worksheet

Baby Size Kitchen Staples Calculator

Inputs
Start from

Completed weeks since the first day of your last period, from 10 to 40.

Result

Calculating…

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

Please note: This calculator gives a general screening estimate, not a diagnosis. Talk to a qualified healthcare professional about your individual health.

What this calculator does

Find a kitchen staple that weighs about the same as a typical baby at your week of pregnancy. Pick your week, or enter your last period or due date. You get the closest match, from a small egg to a gallon of milk, and a chart for every week from 10 to 40.

The baby's weight is a typical average for the week, not a measurement of your baby. Babies vary a lot, and only an ultrasound by your healthcare provider measures your own baby. The food weights come from the U.S. Department of Agriculture (USDA) and from standard package sizes.

Where it's used

Why this math matters outside the classroom:

  • Baking by weight. Bakers swap 2 cups of all-purpose flour for 250 g on a scale, using 125 g per cup.
  • Counting cups. Cooks find a 5-pound bag of flour holds about 18 cups, since 2,268 g ÷ 125 g is about 18.1.
  • Butter math. A recipe calling for 1 cup of butter needs 2 sticks, since each stick is 113 g and a cup is 227 g.
  • Comparing weights. Students divide a typical 23-week weight of 568 g by 680 g of eggs to get a ratio of about 0.83.

How to use it

  1. Choose how to start: the week you're in, the first day of your last period, or your due date.
  2. Enter the week (10 to 40) or the date. For the date options, "Counting from" starts as today; change it to check another day.
  3. Read the closest kitchen staple. Below it is the ratio, the typical weight and the typical length.
  4. Open the table to see the matching staple for every week.

What the inputs mean

Week of pregnancy
Completed weeks since the first day of your last period. For example, 23 weeks 3 days counts as week 23.
First day of last period
The first day of bleeding of your most recent period. The calculator assumes a 28-day cycle.
Estimated due date
The date your healthcare provider gave you, or one from a due date calculator.
Counting from
The day to work out the week for. It starts as today.

Formula and method

Weeks pregnant = days since the first day of the last period ÷ 7
Typical weight (g) = e^(0.578 + 0.332 × W − 0.00354 × W²)
Ratio = typical weight ÷ staple weight
Fair match when the ratio is between 0.67 and 1.5

W is the number of completed weeks of pregnancy. The letter e is a fixed number, about 2.718. The weight formula comes from Hadlock and colleagues (1991) and gives the middle weight for each week.

The ratio compares the two weights. A ratio of 1 means the same weight, and 0.8 means the baby weighs 80% as much. The calculator picks the staple with the ratio nearest to 1, judged by proportion.

If even the nearest staple were more than 1.5 times heavier or lighter, the page would say there's no close match instead.

Worked example

The first day of the last period was March 2, 2026. How does a typical baby compare on August 13, 2026?

  1. Days so far: Aug 13, 2026 − Mar 2, 2026 = 164 days.
  2. 164 ÷ 7 = 23 weeks, 3 days. That's 23 completed weeks, so week 23 is used.
  3. Weight formula: 0.578 + 0.332 × 23 − 0.00354 × 23² = 6.3413, and e^6.3413 = 568 g.
  4. The nearest staple is a dozen large eggs in their shells at 680.39 g. Ratio: 568 ÷ 680.39 = 0.83.
  5. 0.83 is between 0.67 and 1.5, so it's a fair match.

Result: At 23 weeks, 3 days, a typical baby weighs about 568 g (1 lb 4.0 oz), about 83% of the weight of a dozen large eggs.

Understanding the result

A cup measures space, not weight. That's why a cup of flour, a cup of sugar and a cup of honey weigh such different amounts: 125 g, 200 g and 339 g in the USDA's figures. Flour is light and airy, while honey is thick and dense.

A pound of flour is about 3.6 cups, since 453.6 g ÷ 125 g is 3.63. A 5-pound bag holds roughly 18 cups. How you fill the cup matters too. Scooping packs flour in, so a scooped cup often weighs more than a spooned one.

Eggs are sized by weight, not by how they look. In U.S. grading, a dozen large eggs must weigh at least 24 ounces, shells included. One large egg, cracked open, weighs about 50 g.

Packages show a net weight, which is the food alone. A stick of butter is a quarter pound, and a box of pasta is usually one pound.

Assumptions and limitations

  • Cup, stick and egg weights are USDA FoodData Central figures. Single eggs are weighed without the shell; the dozen uses the USDA grading minimum with shells.
  • Bags and boxes use their labeled net weight, without packaging. A gallon of milk is 4 times the USDA quart, 976 g.
  • The week is counted from the first day of the last period, with a due date 280 days after that day. From 41 to 42 weeks 6 days, the 40-week figures are shown.
  • These are averages, not a measurement or a prediction for any one baby. Twins and other multiples are often smaller.
  • The match uses weight only, not size or shape.
  • A cup of flour or sugar at home may weigh a little more or less, depending on how you fill it.
  • It is not a medical tool. It can't detect any problem, and it doesn't replace prenatal care.

Frequently asked questions

Why do single eggs leave out the shell but the dozen doesn't?

Each figure comes from its own source. The USDA food data weighs the egg you'd cook with, without the shell. Egg grading weighs a dozen whole eggs as sold, so the shells count there.

Why does the match jump from a quart of milk to a 4-pound bag of sugar?

There's no common staple between them in the list. The jump happens at week 29, when a typical 1,379 g baby is nearer the 1,814 g bag of sugar than the 976 g quart.

Is my baby too big or too small if my scan shows a different weight?

This page can't tell you that. The weight here is an average, and healthy babies vary widely around it. Ultrasound weights are estimates too. Your healthcare provider looks at your scans and history together, so ask them.

Are the dates I enter stored or shared?

No. The math runs in your browser, and this calculator doesn't create a shareable link with your dates.

How this calculator is checked

Method: Typical weight: Hadlock, Harrist & Martinez-Poyer, Radiology 1991;181:129–33, 50th-percentile equation (10–40 weeks), with lengths and dating as in src/lib/health/fetal-size.ts. Staple weights: USDA FoodData Central SR Legacy portion weights (eggs, butter, flour, sugar, honey, milk) cited by food ID in items.ts; labeled net weights for packages; USDA AMS shell egg weight classes for a dozen large eggs. Matching: closest weight on a ratio scale, with a 1.5× limit. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-26. Found a problem? Tell us.

Embed this calculator

Put this Baby Size Kitchen Staples Calculator on your own website or blog for free. Paste this code where you want it to appear: