Marginal Propensity to Consume (MPC) Calculator

Inputs

Enter direct changes (Δ values)

Change in Income (ΔY)

Change in Consumption (ΔC)

Or enter before / after levels

Income before (Y₁)

Income after (Y₂)

Consumption before (C₁)

Consumption after (C₂)

ΔY = Y₂ − Y₁ and ΔC = C₂ − C₁

—

MPC (ΔC / ΔY)

—

MPS (1 − MPC)

Observations

Scenario Table

#	ΔIncome (ΔY)	ΔConsumption (ΔC)	MPC (ΔC/ΔY)	Action

Example Data

This example shows typical positive ΔY with corresponding ΔC. You can load these rows into the scenario table for instant visualization and metrics.

#	ΔIncome (ΔY)	ΔConsumption (ΔC)	MPC
1	1000	700	0.7000
2	1200	800	0.6667
3	800	520	0.6500
4	1500	975	0.6500
5	900	585	0.6500

Formula Used

The marginal propensity to consume (MPC) measures how much consumption changes for a one unit change in income:

MPC = ΔC / ΔY

ΔC: Change in consumption between two periods.
ΔY: Change in income between the same two periods.

The marginal propensity to save (MPS) complements MPC:

MPS = 1 − MPC

For multiple observations, an overall MPC can be approximated as the ratio of totals: MPC_total = ΣΔC / ΣΔY. When modeling consumption with zero intercept, the slope estimate is also Σ(ΔY·ΔC) / Σ(ΔY²).

How to Use This Calculator

Enter ΔIncome and ΔConsumption directly, or use the before/after fields and click Fill Δ from levels.
Click Add to scenarios to place the current Δ values into the table.
Use Load example data to pre-populate realistic observations.
Review the MPC and MPS KPIs above the table; they update as you edit rows.
View the scatter and fitted line in the chart.
Export your table and metrics using Download CSV or Download PDF.
Use the results in homework, research notes, or quick sensitivity analysis.

Tip: MPC typically lies between 0 and 1. If ΔY ≤ 0 your MPC may be undefined or negative; interpret with care.

FAQs

MPC tells you how much extra people spend when their income rises. If MPC = 0.7, a 100 increase in income raises consumption by 70 on average.

MPC uses changes between two points, while average propensity to consume uses levels (C/Y). MPC focuses on the incremental response to income shifts.

It is uncommon but possible in short runs if consumption rises more than income, perhaps due to borrowing or drawing down savings. Sustained MPC > 1 is typically not stable.

MPC becomes undefined because you would divide by zero. You should remove or adjust those rows when computing an overall MPC.

The line passes through the origin with slope equal to the current overall MPC (ΣΔC / ΣΔY). It represents predicted ΔC for any given ΔY.

Yes. If income falls (negative ΔY), the sign of MPC reflects whether consumption falls or rises. Interpret negative or extreme values carefully.

A robust summary uses totals (ΣΔC / ΣΔY). If theory implies no intercept, a slope estimate Σ(ΔY·ΔC) / Σ(ΔY²) is another option for your analysis.

Visualization

Points show each scenario (ΔY, ΔC). The line shows predicted ΔC given current MPC.

Notes

Edit values directly inside the scenario table cells.
KPIs and the chart refresh automatically on change.
Hover the chart to read precise coordinates.

Inputs

Scenario Table

Example Data

Formula Used

How to Use This Calculator

FAQs

What is MPC in plain terms?

How is MPC different from average propensity to consume?

Can MPC be greater than 1?

What if ΔY equals zero?

How is the line in the chart determined?

Does this handle negative changes?

Is there a best way to aggregate?

Visualization

Notes

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