Material Substitution Calculator

Convert a quantity of one material into the equivalent amount of a substitute, using a yield or coverage ratio you supply.

General Crafting

Substituting one material for another is arithmetic once you know the ratio, and the ratio is the part only you can supply: a yarn of a different weight, a fabric of a different width, a dye of a different strength, a sheet of a different thickness. This calculator takes the quantity, the ratio and the prices, returns the substitute quantity and the packs to buy, and states the ratio it used so the assumption is on the page rather than in your head.

At a glance

What you enter: Quantity of the original material, Substitute per one unit of the original, Cost per unit of the original, Cost per unit of the substitute, Waste and sample allowance, Substitute in one pack, Price per pack
What you get: Substitute quantity, Change in quantity, Cost of the original material, Cost of the substitute material, Difference in cost, Change in cost, Break-even ratio, Substitute to buy, Packs to buy, Substitute you will own, Surplus after the project, Cost of the substitute order, Substitute cost per original unit, The substitution is cheaper at the unit costs, Ratio used in this calculation
Formula shown: Yes, every step, right below your results.
Cost and privacy: Free, no account needed, and nothing you type is stored.

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Quantity of the original material units

Metres, grams, sheets, millilitres. The same unit the ratio is expressed in.

Substitute per one unit of the original times

If one metre of the original becomes 1.25 metres of the substitute, the ratio is 1.25. It is material specific, so measure it rather than assuming it.

Cost per unit of the original

Cost per unit of the substitute

Waste and sample allowance %

Offcuts, a re-cut and a test piece. Applied to the substitute quantity.

Substitute in one pack units

Leave at zero if the material is sold by continuous length or weight.

Price per pack

Used for the order cost when a pack size is entered.

Reset

Results are estimates for general information only, always verify with a professional or official source before acting on them.

How to use the Material Substitution Calculator

1 Enter Quantity of the original material (units), Metres, grams, sheets, millilitres. The same unit the ratio is expressed in.
2 Enter Substitute per one unit of the original (times), If one metre of the original becomes 1.25 metres of the substitute, the ratio is 1.25. It is material specific, so measure it rather than assuming it.
3 Enter Cost per unit of the original
4 Enter Cost per unit of the substitute
5 Enter Waste and sample allowance (%), Offcuts, a re-cut and a test piece. Applied to the substitute quantity.
6 Enter Substitute in one pack (units), Leave at zero if the material is sold by continuous length or weight.
7 Enter Price per pack, Used for the order cost when a pack size is entered.
8 Press Calculate. You get Substitute quantity, Change in quantity, Cost of the original material, Cost of the substitute material, Difference in cost, Change in cost, Break-even ratio, Substitute to buy, Packs to buy, Substitute you will own, Surplus after the project, Cost of the substitute order, Substitute cost per original unit, The substitution is cheaper at the unit costs, Ratio used in this calculation, and every intermediate step stays visible under "How is this calculated?"
9 Change one number at a time to see what moves the result, that is usually the most useful thing a calculator can tell you.

Worked examples

Real numbers run through this calculator. Open any example to load it into the form above and change it.

Ten metres of a heavier substitute

A substitute that needs 1.25 metres for every metre of the original, at 10 a metre against 8.

You enter

Quantity of the original material: 10 units
Substitute per one unit of the original: 1.25 times
Cost per unit of the original: $8.00
Cost per unit of the substitute: $10.00
Waste and sample allowance: 10%
Substitute in one pack: 5 units
Price per pack: $45.00

You get

Substitute quantity: 12.50 units
Change in quantity: 25.0%
Cost of the original material: $80.00
Cost of the substitute material: $125.00
Difference in cost: $45.00
Change in cost: 56.3%
Break-even ratio: 0.80
Substitute to buy: 13.75 units
Packs to buy: 3
Substitute you will own: 15.00 units
Surplus after the project: 1.25 units
Cost of the substitute order: $135.00
Substitute cost per original unit: $13.50
The substitution is cheaper at the unit costs: 0
Ratio used in this calculation: 1.25

12.5 metres of substitute, so 13.75 with the waste, which is three packs of 5 and 1.25 metres of surplus. The cost goes from 80 to 135, a 69 percent increase, and the break-even ratio is 0.8.

Open this example in the calculator →

A wider fabric at the same price

One hundred and twelve centimetres replaced by 140 cm, area matched.

You enter

Quantity of the original material: 10 units
Substitute per one unit of the original: 0.80 times
Cost per unit of the original: $8.00
Cost per unit of the substitute: $8.00
Waste and sample allowance: 10%
Substitute in one pack: 0 units
Price per pack: $0.00

You get

Substitute quantity: 8.00 units
Change in quantity: -20.0%
Cost of the original material: $80.00
Cost of the substitute material: $64.00
Difference in cost: $-16.00
Change in cost: -20.0%
Break-even ratio: 1.00
Substitute to buy: 8.80 units
Packs to buy: 0
Substitute you will own: 0.00 units
Surplus after the project: -8.80 units
Cost of the substitute order: $64.00
Substitute cost per original unit: $6.40
The substitution is cheaper at the unit costs: 1
Ratio used in this calculation: 0.80

Eight metres become 8.8 with the waste, so the cost falls from 80 to 70.40: the substitution saves 12 percent without the substitute being cheaper per metre. This only holds if the pattern pieces fit the wider cloth without a directional constraint.

Open this example in the calculator →

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Frequently asked questions

How do I work out the ratio for a yarn substitution?

Work a swatch in the substitute and compare the fabric it makes with the original. If the substitute covers 10 percent less area per metre, the ratio is about 1.11 for the same area, or about 1.23 if the shortfall is in both directions, so 10 balls of the original becomes 11 or 12 of the substitute. The yarn weight class tells you what is worth trying, not how much you will need, and a mill ended or hand dyed yarn can differ from its nominal count.

What ratio do I use for a different fabric width?

If you are matching area and the substitute is wider, divide the original width by the substitute width: 112 cm replaced by 140 cm gives a ratio of 0.8, so 10 metres becomes 8. If the fabric has a nap, a one way print or a directional pile, the ratio is 1 whatever the width, because every metre still has to be cut the same way. Check that the pattern pieces actually fit the new width before you rely on the arithmetic.

Is a cheaper material actually cheaper?

Only if it also goes as far. Divide the original unit cost by the substitute unit cost to get the break-even ratio, which is the ratio at which the substitution costs the same. If the original is 8 a unit and the substitute is 10, the break-even ratio is 0.8, so the substitute has to deliver the same work in four fifths of the quantity to be worth it. A substitute that is cheaper per unit but needs more material per project is a dearer substitution, and the shelf price never shows it.

How much waste allowance should I add?

Ten percent for a substitution you have measured on a swatch, and fifteen to twenty for one you are trying for the first time or where the ratio is an estimate. The allowance covers the sample, the offcuts and the piece you cut wrong because the substitute handled differently from the original. It applies to the substitute quantity, not the original, and where the material is bought in dye lots it is worth buying the upper end of your estimate rather than risking a lot that cannot be matched.