Nutrition data
Nutrition values come from USDA FoodData Central, the food composition database of the United States Department of Agriculture. 151 of the 155 foods use its SR Legacy data and 4 use its Foundation Foods data.
USDA reports values per 100 g of food. Food pages show them per 100 g, and per $1 values are worked out from them. The 155 foods are raw or dry staples in 8 groups. Where USDA has no entry for a food, a similar entry is used and the food page says so (4 foods). 9 foods share one entry with a similar food, and their pages say that too.
A sample of 42 foods was checked against the New Zealand Food Composition Database (FOODfiles), and most agreed within normal variation between samples.
Price research
Brisbane prices are checked in person at local shops by me, or researched from local supermarket prices. Prices for other locations come from shoppers who add what they paid. Every price is saved as price per kg.
- Step 1CollectDraft from data, for reviewShoppers add the pack price, pack size, store type and date. New prices start as pending.
- Step 2CheckDraft from data, for reviewEach price is reviewed. A price more than twice, or less than half, the approved median for that food and location is flagged for a closer look.
- Step 3PublishDraft from data, for reviewApproved prices for each food and location are combined into a median. A location appears on the site once it has 5 approved submissions.
The per-dollar formula
To compare foods by value, the site works out how much of a nutrient $1 buys. A food that is cheap for the nutrient it has ranks high, even if another food has more of that nutrient per 100 g.
Loading Brisbane prices.
Approximate. Adjusted for the share of the cut that is meat rather than bone. See how I estimate this.
Rounding: values of 10 or more show as whole numbers, values under 10 show to one decimal, and an exact zero shows as 0. Switching between kg and lb only changes how prices are shown. Values per $1 stay the same.
Your own prices
On a food page, you can type the price you pay. Every figure on that page is worked out again with your price. It is not saved or sent anywhere.
On Add prices, you see your own ranking as soon as you submit. Your prices are saved as pending. They only change the prices on the site after they are reviewed, and once your location has 5 approved submissions.
Assumptions and estimates
Some numbers on this site are estimates or choices I made. I list them all here so you can judge how far to trust them.
Bone-in cuts (marked with *)
USDA nutrition values are for the meat you eat. Shop prices are for the weight you buy, bones included. For the cuts below I adjusted the per $1 figures by the share of the cut that is meat. These shares are approximate, and any figure that uses one is marked with an asterisk.
| Food | Edible share I use | Where it comes from |
|---|---|---|
| Chicken drumstick | 57% | USDA Agricultural Marketing Service standard yield for drumsticks with skin and bone removed. |
| Whole chicken | 65% | My estimate of the meat and skin share of a whole bird. |
| Chicken wing | 40% | My estimate. Wings are mostly bone and skin, and the nutrition values I use are for meat only. I did not find an official figure. |
| Lamb chops | 75% | My estimate of the share left after the bone. The price is an average of BBQ chops and loin chops. |
| Pork loin | 90% | My estimate. The price is an average of bone-in loin chops and a boneless roast. |
Peel, stones, shells and cores
Fruit and vegetables are priced by the weight you buy, including peel, stones, cores and rind, but USDA values are for the part you eat. I have not adjusted these yet, so their per $1 figures are higher than what the edible part gives you. This matters most for melons, pineapple, mango, avocado, bananas, oranges and corn on the cob. Seafood sold in the shell would have the same issue.
Estimated weights
Where a shop sells a food each or by the bunch and the label gives no weight, I use a typical weight. Examples are 120 g for a lemon, 1.2 kg for a rockmelon, 1.5 kg for a pineapple, 450 g for a mango, 200 g for an avocado and 1 kg for a cauliflower. These make the price per kg approximate.
Egg whites and yolks
I work out egg white and egg yolk prices from the whole egg price. A white is 58% of an in-shell egg and a yolk is 31%, using USDA figures. I assume the other part is wasted, so these are not shelf prices.
Researched and verified prices
Prices marked Researched are averages of prices I found for several shops, not prices I checked in person. Prices marked Verified in person are shelf tickets I photographed, averaged where I found more than one. Both cover a small number of shops, mainly Coles and ALDI, and shelf prices change from week to week.
Similar USDA entries
Where USDA has no entry for a food, I use a similar one, and the food page says so.
Updates and limits
Brisbane prices are checked in person or researched, and updated when I re-check them. Prices for other locations come from approved shopper submissions. Nutrition values come from USDA FoodData Central and do not change often.
USDA values describe foods sold in the United States. Foods in Australia and New Zealand can differ. For example, New Zealand soils are low in selenium, so New Zealand meat can have less selenium. Food composition tables in Australia and New Zealand also calculate energy differently, so legumes and grains can show fewer calories there. Rules for adding vitamins to foods, such as folic acid in bread flour, also differ between countries.
Values are for each food as described in its USDA entry, such as raw or dry, not as cooked or served. Prices are medians of the prices collected for a location and change from shop to shop and week to week.
My estimates and assumptions are listed under Assumptions and estimates.
This site compares nutrients and prices. It does not give health or diet advice.