Free · Elasticity and market changes

Supply Elasticity: Base-Period & Midpoint Methods

Calculate signed supply elasticity from two prices and quantities, with base-period and midpoint percentage-change options.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

Price increasing from 10 to 12 and supply from 100 to 140 gives base-period elasticity of 2. Supply changes 40% while price changes 20%.

Supply elasticity = relative quantity-supplied change / relative price change

Worked example

Enter these known values and leave the other values blank.

Initial price
10 USD
Final price
12 USD
Initial quantity supplied
100
Final quantity supplied
140
Price change by chosen method
20 %
Quantity change by chosen method
40 %
Signed supply elasticity
2

Assumptions and limitations

  • Prices and initial quantity must be positive; final quantity may be zero. Price change must be nonzero.
  • Base-period change divides by the initial value; midpoint change divides by the average endpoint value. Use the same method for both variables.
  • This finite change is not a point derivative. Changes in technology, costs, timing or other conditions can affect the observed relationship.
  • Use matching periods, currency and quantity units. Currency selectors use captured fixed exchange rates, not live rates.

Common questions

What does a negative result mean?

It records opposite directions of change. The calculator does not establish why the observations moved that way.

Can supply stay unchanged?

Yes. When prices differ and quantities match, the elasticity is zero.

References

Use separate base-period and midpoint inverse formulas so midpoint endpoints do not divide by the zero base-period coefficient. Allow zero final supply and require feasible method-specific changes, with nonzero price change and precise elasticity classifications.

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