Price Elasticity of Supply Calculator - Arc PES
Measure how quantity supplied responds to a price change.
Enter the initial and final price together with the initial and final quantity supplied.
About the Price Elasticity of Supply Calculator
Price elasticity of supply measures how quantity supplied responds when price changes. Producers who can expand output quickly, such as digital goods or inventories already on hand, tend to show elastic supply. Producers bound by capacity, land, or long training times tend to show inelastic supply. The price elasticity of supply calculator uses the midpoint, or arc, formula and then takes the absolute value, so the reported PES is never negative. Formula: PES = |[(Q2 − Q1) / ((Q1 + Q2) / 2)] ÷ [(P2 − P1) / ((P1 + P2) / 2)]|. Supply change % = (Q2 / Q1 − 1) × 100 and price change % = (P2 / P1 − 1) × 100 use the initial observation as the base. Those supporting percentages keep their sign, even though PES itself is unsigned. PES above 1 is elastic supply; below 1 is inelastic; equal to 1 is unit elastic. All four inputs must be positive. Taking the absolute value is a textbook convention for supply, where price and quantity usually move together. If your data show quantity falling as price rises, the signed ratio would be negative, but this calculator still reports a positive PES. Inspect the supply-change and price-change percentages to see the direction of each move. Arc elasticity is appropriate for discrete observed changes; it is not a local derivative along a smooth supply curve. Use the price elasticity of supply calculator to compare a harvest-season response with an off-season response, or to see whether a supplier can match a retailer’s planned price increase. Short-run supply is often less elastic than long-run supply because capital can be adjusted only over time. The result is an analytical ratio, not a commitment that a factory will ship the implied extra units. Keep both observations in the same unit and period definition, and treat the output as a planning aid rather than a forecast.
Price elasticity of supply examples
Arc PES values reported as absolute numbers.
| Inputs | Output | Note |
|---|---|---|
| Price $10 to $12; quantity 100 to 120 | PES 1; supply 20.00%; price 20.00% | Midpoint percentages match, so supply is unit elastic. |
| Price $10 to $20; quantity 100 to 150 | PES 0.6; supply 50.00%; price 100.00% | Quantity rises less than price on a midpoint basis, so supply is inelastic. |
| Price $8 to $10; quantity 50 to 80 | PES 2.0769; supply 60.00%; price 25.00% | Quantity is highly responsive over this range. |
How to calculate price elasticity of supply
- Gather two comparable observations of price and quantity supplied.
- Enter initial and final price and initial and final quantity.
- Select Calculate to review absolute arc PES plus the simple percent changes.
- Classify the result as elastic, inelastic, or unit elastic using 1 as the benchmark.
Price elasticity of supply FAQ
Why is PES always positive?
The calculator takes the absolute value of the midpoint ratio. Supply is conventionally reported as a positive number even if a particular data pair moves in opposite directions.
Is this the midpoint formula?
Yes. The PES ratio uses average price and average quantity. The separate supply-change and price-change percentages still use the initial observation as the base.
What is unit-elastic supply?
PES equals 1 when the midpoint percent change in quantity equals the midpoint percent change in price. The two observations then sit on a unit-elastic arc.
Can I compare short-run and long-run supply?
Yes, if you have two pairs of observations for each horizon. Long-run pairs often show a higher PES because plants and hiring can adjust.
Is this a production forecast?
No. Elasticity summarizes two points. Capacity, input costs, and regulation can prevent a supplier from delivering the quantity a ratio might suggest.