To cost a recipe properly, everything has to end up in the same unit your recipe uses: grams for what you weigh, millilitres for what you pour, and units for what you count. The step is always the same: price paid ÷ amount in the pack, in that unit. Anything that does not come in kilos or litres, such as bunches, dozens or cups, gets weighed or counted once and written down for good.
Pick three base units
Work with just three units:
- Grams (g) for anything you weigh: flour, oats, butter, nuts, sugar, fruit.
- Millilitres (ml) for liquids: oil, milk, vinegar, water.
- Units for things you count and use whole: eggs, jars, labels, bags.
Why grams rather than kilos? Because recipes use small amounts. With a price per gram, any quantity in the recipe is one multiplication away, whether you bought the nuts by the kilo, by the pound or in a small bag.
The formula
Price per base unit = price paid ÷ amount in that unit
Cost in the recipe = price per base unit × amount you use
A 1 kg bag of oats at $3.20 gives 3.20 ÷ 1,000 = $0.0032 per gram. If the recipe uses 540 g: 0.0032 × 540 = $1.73.
Do not round the price per gram. Almonds at $0.0176 per gram rounded to $0.02 look almost the same, but 0.02 ÷ 0.0176 = 1.14, so you overstate them by about 14%. Keep three or four decimals and round only the result.
Conversion table
| If you buy by the... | To cost it |
|---|---|
| Kilo | 1 kg = 1,000 g |
| Pound | 1 lb = 453.6 g |
| Ounce (weight) | 1 oz = 28.35 g |
| Litre | 1 L = 1,000 ml |
| Fluid ounce, pint, gallon | Use the ml printed on the label; US and UK sizes differ |
| Dozen | 12 units |
| Tray or case | Count what is in it |
| Pack, tin, bag | Read the weight or volume on the label, every time |
| Sack | The weight on the sack; weigh loose produce yourself |
| Bunch (coriander, parsley, mint) | Weigh it trimmed, only the part you use |
| Cup, tablespoon, teaspoon | Measure your own with each ingredient and note the grams |
Cups and spoons
A cup is a measure of volume, not weight. A cup of flour and a cup of sugar take up the same space but do not weigh the same. And cups are not all the same size: yours may be bigger or smaller than the one in the recipe you copied.
The fix is to measure once. Fill your cup or spoon with the ingredient the way you always do, and weigh it. Write "1 cup oats = so many grams" on your recipe. For liquids, a measuring jug gives you millilitres directly. With water, a millilitre weighs practically a gram; oil weighs a little less and honey quite a lot more, so do not swap one for the other.
Once you have the measurements, the best move is to rewrite the whole recipe in grams. A recipe written by weight costs more accurately and comes out the same every time. How to write a standard recipe card has the format.
Things bought by the piece or by the bunch
Lemons, bananas, onions, avocados: sold by weight or by the piece, while the recipe says "3 bananas". Weigh ten, divide by ten, and you have the average weight of one. Now "3 bananas" becomes grams.
Eggs work the other way: you buy a dozen or a tray and use them one at a time, or only the whites. Price per egg is the pack price divided by the count.
Bunches vary most. A bunch of coriander from one stall does not weigh the same as from another, or in every season. Weigh it when you change supplier or when it looks thinner than usual.
Worked example: a batch of granola
You make granola in batches. Every ingredient comes in a different unit, and the recipe you started from is written in cups.
| Ingredient | How you buy it | Price per base unit | You use | Cost |
|---|---|---|---|---|
| Rolled oats | 1 kg bag at $3.20 | $0.0032 per g | 6 cups, weighed at 90 g each = 540 g | $1.73 |
| Honey | 500 g jar at $6.50 | $0.013 per g | ½ cup, weighed = 170 g | $2.21 |
| Almonds | 1 lb bag at $7.99 | $0.0176 per g | 200 g | $3.52 |
| Sunflower oil | 1 L bottle at $3.60 | $0.0036 per ml | ½ cup, measured = 120 ml | $0.43 |
| Eggs | Dozen at $4.20 | $0.35 each | 2 (whites only) | $0.70 |
| Cinnamon | 50 g jar at $2.50 | $0.05 per g | 2 tsp, weighed = 5 g | $0.25 |
| Batch total | $8.84 |
The sums, one by one:
- Oats: 3.20 ÷ 1,000 = 0.0032; 0.0032 × 540 = 1.728
- Honey: 6.50 ÷ 500 = 0.013; 0.013 × 170 = 2.21
- Almonds: 7.99 ÷ 453.6 = 0.0176; 0.0176 × 200 = 3.52
- Oil: 3.60 ÷ 1,000 = 0.0036; 0.0036 × 120 = 0.432
- Eggs: 4.20 ÷ 12 = 0.35; 0.35 × 2 = 0.70
- Cinnamon: 2.50 ÷ 50 = 0.05; 0.05 × 5 = 0.25
- Total: 1.728 + 2.21 + 3.52 + 0.432 + 0.70 + 0.25 = 8.84
The batch makes about 1 kg, which you pack into three 330 g bags: 8.84 ÷ 3 = $2.95 of ingredients per bag. Packaging, your time and the oven still need adding for the loaded cost; going from batch to unit is covered in how to calculate the cost per unit of a recipe.
One detail: the almonds are costed at the weight you bought. If a recipe called for "200 g of chopped, toasted almonds" and you lost some to the board, you would need to buy more than 200 g. That adjustment is explained in how to cost an ingredient you buy by the package.
The mistakes that keep coming back
- Mixing kilos and grams. Multiply cheese at $12.00 a kilo by 400 g without converting first and you get $4,800 of cheese. It is a thousand-fold error, easy to catch if you check that each number makes sense.
- Trusting last month's label. Packs shrink and the price sometimes stays put. Read the weight every time you buy.
- Leaving "a cup" unmeasured. Each time someone fills the cup a little differently, both the cost and the taste change.
- Counting pieces without weighing them. A banana in one delivery is not the same size as a banana in the next.
- Mixing bought weight and trimmed weight. Price one way, recipe the other, and the cost comes out short.
All of this sits inside the full method in how to calculate the cost of a food product.
Do it with the calculator
In the food cost calculator, enter each ingredient with what you paid and the pack size in kilos, grams, litres, millilitres or units, plus what the batch uses; it converts between kilos and grams or litres and millilitres for you. Anything you measure in cups or buy by the bunch, turn into grams first using your own measurement.
Frequently asked questions
How many grams are in a cup?
It depends on the ingredient and on the cup. A cup of flour weighs far less than a cup of sugar, and cups are not the same size everywhere. Fill your own cup with each ingredient you use, weigh it once and write the result down.
How do I cost herbs I buy by the bunch?
Weigh the bunch once it is trimmed, keeping only the part you use, and divide what you paid by those grams. Bunches vary by seller and season, so weigh again from time to time.
How many decimals should I keep in the price per gram?
At least three or four. Rounding $0.0176 per gram to $0.02 looks harmless, but it overstates that ingredient by about 14%. Round only the final result.
Should I use the weight I buy or the weight after trimming?
Use the same weight in the price and in the recipe. If the recipe is written in trimmed weight, work out the price per trimmed gram, which is always higher than the price per gram as bought.