How to Compare Protein Cost Per 100g Supermarket Options

To compare protein cost per 100g supermarket options, divide each product’s price by the grams of protein in the amount that price buys, then multiply by 100. Use the same food basis for every item—such as as-sold, drained or cooked—and record the price and pack size. This gives you a like-for-like protein-cost figure, while a worked example and checklist help you avoid misleading comparisons when planning a Coles shop.

Decide what the comparison is for

Match the question to a real shopping decision

The calculation answers one narrow question: how much the protein costs at the price you recorded. It does not tell you which food tastes better, fits a particular recipe or makes a more balanced meal. For a practical substitution, compare foods that could serve a similar role in the meal you are planning. For a broader budget scan, you can compare across food groups, but treat the ranking as a starting point rather than a recipe recommendation.

Grocery unit prices help compare the cost of different product quantities, but a price per kilogram of food is not the same as a price per 100g of protein. The ACCC explains how unit pricing helps shoppers compare product quantities; the protein calculation is a separate step (ACCC guide to grocery unit prices).

• For a recipe swap: compare options that can perform the same job in that meal.
• For macro planning: check the protein cost alongside the portion’s calories and other macros.
• For a weekly budget: distinguish the amount used in a recipe from the whole pack you must pay for.

Record price, quantity and protein on matching bases

Check what the nutrition figure describes

For packaged foods, note the current shelf or online price, pack quantity and protein per 100g. Nutrition information panels can present values per serving and per 100g; use the per-100g figure when it describes the same food state as the quantity in your calculation. FSANZ outlines the information presented on nutrition panels (FSANZ: nutrition information panels).

For foods without a nutrition panel, a food-composition database can provide a reference value, but choose an entry that matches the food and preparation state as closely as possible. The Australian Food Composition Database provides composition information for Australian foods (FSANZ: Australian Food Composition Database). A database entry is a reference, not a guarantee that every brand or product has an identical value.

Keep the price and protein bases aligned. If you will discard liquid from a can, use the drained quantity and a protein figure for the drained food. If your calculation uses the full pack price, make clear that the quantity represents the edible food bought with that pack. Do not compare a dry weight for one food with a cooked weight for another without accounting for the difference.

• Record whether the price is regular or promotional.
• Write down pack weight, or drained weight when that is the relevant food quantity.
• Note whether protein is listed per 100g as sold, drained or cooked.
• Add the store and date so you can tell when the entry may need checking.

Calculate the cost per 100g of protein

Use pack protein, not the food’s weight alone

First calculate the protein in the quantity represented by the price. Then divide the price by that protein total and multiply by 100:

Protein in quantity (g) = quantity (g) × protein per 100g ÷ 100

Cost per 100g protein = price ÷ protein in quantity (g) × 100

For example, an illustrative 500g pack with 20g protein per 100g contains 100g protein: 500 × 20 ÷ 100. At an illustrative price of $4.00, the result is $4.00 ÷ 100 × 100, or $4.00 per 100g protein. These figures demonstrate the arithmetic; they are not a current product price or claim.

Keep quantities in grams and protein values in grams. If you have a price per kilogram, that price can help compare pack sizes, but you still need the pack quantity and protein information to calculate protein cost. Do not substitute the shelf unit price for the formula above.

Compare options with a worked example

Read the ranking as a screen, not a verdict

The table uses illustrative figures only. Each row assumes its price, quantity and protein value refer to compatible product details. For the tuna example, the quantity is drained weight and the full pack price is used; the calculation assumes the stated protein value is also for drained tuna.

Illustrative example: For lentils, 500 × 24 ÷ 100 gives 120g protein; $2.80 ÷ 120 × 100 gives $2.33 per 100g protein, rounded to the nearest cent. The same formula gives the other rows. Check the basis before trusting the ranking: if the tuna quantity is drained but its protein figure is not, the result is not a sound comparison.

In this illustration, lentils rank lowest on protein cost. That does not make them an automatic replacement for chicken in every meal: they may not suit the same recipe or preparation plan. Australian dietary guidance includes varied protein foods, including legumes, eggs, seafood and meat, so consider where an option fits in the meals you intend to make (Eat for Health: protein foods).

Check the trade-offs the ratio leaves out

Separate protein efficiency from checkout cost

A low protein-cost result can still be a poor fit if you need to buy more than the recipe uses or the remaining food goes unused. For budgeting, record the whole-pack checkout cost. You can also estimate the share used in a meal, but keep the unused amount visible in your plan rather than treating it as free or already consumed.

For meal and macro decisions, check the portion you will actually eat. A lower cost per 100g of protein does not necessarily mean the same meal cost, calorie total or macro balance. This matters when comparing products with different roles or when a recipe calls for different amounts of each option.

• Pack leftovers: ask whether the rest can realistically be used in another planned meal.
• Price changes: mark a special price so it is not mistaken for the regular price next time.
• Food state: keep raw, cooked, drained and as-sold values distinct.
• Meal fit: compare portion cost and macro impact when choosing a substitution.

Use these checks to decide whether a low ratio is useful for your shop, not just whether it is mathematically correct.

Keep a short comparison log and make your first entry

Refresh only when a relevant detail changes

A small log is easier to maintain than a catalogue of every product. Keep the options you buy regularly and close substitutes that could change your decision. Record product, price date, pack size, protein basis and calculated result. Recheck an entry when the price, quantity or nutrition information changes; a past result cannot establish what the product costs at your next shop.

Illustrative starting policy: recalculate when you notice a price or pack-size change. This is a practical trigger, not a universal schedule; adjust it if you find your log is often out of date or if the products you buy rarely change. For online listings, verify that the price and pack size match the item you intend to buy.

Start with one product already on your shopping list: write down its price, quantity and protein figure, confirm the food basis, and calculate its cost per 100g protein. Then compare one realistic alternative and check both whole-pack cost and meal fit. If you want to connect macro targets with planned meals and supermarket costs, Macronomics is designed for Coles shoppers, with capabilities including whole-pack cost estimates and protein-cost comparisons. You can visit Macronomics to learn about its staged beta.

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