ποΈ MPC Calculator: Marginal Propensity to Consume
What share of new income gets spent versus saved.
Marginal propensity to consume
Estimates for planning only, not financial advice.
Marginal propensity to consume is the fraction of each new dollar that gets spent: change in consumption divided by change in income. A $1,000 income gain that lifts spending by $750 gives an MPC of 0.75, which means the marginal propensity to save is 0.25 and the Keynesian multiplier is 4. This calculator computes MPC, MPS, and the multiplier from your income and spending changes.
MPC is the hinge of macroeconomics. It decides whether stimulus multiplies through the economy or sits in savings accounts, whether tax cuts boost demand or asset prices, and how deep a downturn runs. One ratio, enormous consequences.
How to Use This Calculator
Enter the change in disposable income and the resulting change in consumption over the same period. The calculator returns MPC, MPS, the multiplier, and the saved amount.
Enter the change in disposable income: a raise, bonus, or stimulus amount.
Enter how much of it was spent rather than saved.
Read MPC, MPS, and the multiplier. For the inflation that stimulus can bring, our inflation calculator shows the purchasing-power side.
The Formulas
The multiplier is the elegant part: each round of spending becomes someone's income, of which MPC is respent, forming a geometric series that sums to 1/(1-MPC). With MPC of 0.75, $1,000 of stimulus becomes $750 of second-round spending, $562.50 of third-round, and so on to $4,000 total. The series converges because every round leaks savings.
MPC Across Households
| Group | Typical MPC | Multiplier | Policy implication |
|---|---|---|---|
| Low income | 0.85 to 0.95 | 6.7x to 20x | Stimulus multiplies strongly |
| Middle income | 0.60 to 0.80 | 2.5x to 5x | Moderate multiplier |
| High income | 0.30 to 0.50 | 1.4x to 2x | Mostly saved, weak stimulus |
The gradient is the whole argument for targeted stimulus: a dollar sent to a constrained household circulates many times, while a dollar sent to a wealthy one parks in assets. Real-world multipliers run lower than the textbook figures because of taxes, imports, and timing, but the ordering holds. For personal saving behavior behind the aggregate, our savings calculator models the MPS side of household budgets.
Worked Example
With the defaults: income rises $1,000, consumption rises $750. MPC is 750 / 1,000 = 0.75. MPS is 1 - 0.75 = 0.25. The multiplier is 1 / 0.25 = 4.00x. Saved from the new income is $250. The spending rounds play out as 750 + 562.50 + 421.88 + 316.41 and onward, converging on $4,000 of total economic activity from the initial $1,000.
Limits of the Multiplier
The textbook multiplier assumes idle capacity, no inflation response, and no offsetting imports or taxes. Near full employment, stimulus mostly bids up prices instead of output. Open economies leak spending to imports each round. And Ricardian skeptics argue households save stimulus anticipating future taxes, shrinking MPC directly. The multiplier is a useful first approximation, not a promise.
My rule: use MPC thinking for direction and relative comparisons, never for precise forecasts. Knowing that targeting the constrained beats targeting the comfortable holds up; claiming the multiplier is exactly 4.0 is not.
MPC in Your Own Budget
The macro concept has a personal twin: your own marginal propensity to consume. Track what happens to the next $1,000 that arrives, a bonus, a tax refund, a raise. If $800 gets spent, your personal MPC is 0.8, and knowing it honestly is the first step to changing it. Most households discover their MPC is higher than they guessed, because lifestyle spending absorbs raises automatically.
To lower your personal MPC, intercept the money before it reaches checking: raise 401(k) contributions or automatic transfers the same week the raise hits. Lifestyle lag, deliberately living on last year's income for a year, is the most powerful technique because it converts the entire raise into savings. The macro paradox of thrift does not apply to you: one household saving more does not shrink the economy, it just builds wealth. For the savings destination, our savings calculator projects the payoff.
The Multiplier in Real Crises
The 2020 stimulus checks were a live MPC experiment. Studies found households spent roughly 30 to 40 percent within months, an MPC of 0.3 to 0.4, lower than textbook assumptions because uncertainty was extreme and spending options were limited. The 2008 rebates showed higher MPCs around 0.5 to 0.7, spent faster by lower-income households, exactly as theory predicts.
These results refined policy: later support tilted toward unemployment benefits and targeted transfers, which carry higher MPCs than universal checks. The lesson for forecasters is that MPC is not a constant but a function of confidence, constraints, and the economic weather. Models that treat it as fixed overshoot stimulus effects in panics and undershoot them in confident expansions. For the inflation that follows large stimulus, our inflation calculator tracks the purchasing-power aftermath.
Estimates for planning only, not financial advice.Frequently Asked Questions
What is marginal propensity to consume?
The share of each additional dollar of income that gets spent: the change in consumption divided by the change in income. If a $1,000 raise lifts spending by $750, MPC is 0.75. It is the central behavioral parameter in Keynesian economics, driving the multiplier effect.
How do you calculate MPC?
Divide the change in consumption by the change in disposable income. Both changes must be measured over the same period from the same data. An MPC of 0.75 means 75 cents of every new dollar is spent and 25 cents saved, which is also the marginal propensity to save, MPS = 1 - MPC.
What is the relationship between MPC and MPS?
They sum to 1: every new dollar is either spent or saved. MPC of 0.75 implies MPS of 0.25. This calculator shows both from your inputs, so the mps question is answered on the same page: the marginal propensity to save is simply one minus the propensity to consume.
What is the Keynesian multiplier?
One divided by MPS: the total GDP impact of an initial spending injection. With MPC of 0.75 and MPS of 0.25, the multiplier is 4, so $1 billion of government spending theoretically generates $4 billion of total economic activity as the money is respent round after round. Higher MPC means a bigger multiplier.
Who has the highest MPC?
Lower-income households, who spend nearly all of additional income on necessities. Studies consistently find MPC near 0.9 or higher for the bottom quintile and much lower for the wealthy. This is why stimulus targeted at lower incomes multiplies through the economy fastest.
Can MPC be greater than 1?
Temporarily, yes: households can spend more than the income gain by borrowing or drawing savings, common when stimulus arrives during hardship. Sustained MPC above 1 is impossible in aggregate without rising debt. The calculator constrains inputs to the standard 0-to-1 range for the textbook case.
How does MPC affect fiscal policy?
It determines the bang per buck of stimulus. Tax cuts for high earners with low MPC mostly get saved, multiplying little; transfers to low earners with high MPC get spent and respent. Policymakers use MPC estimates to target stimulus where the multiplier is largest.
What is the paradox of thrift?
If everyone tries to save more at once, spending falls, incomes fall, and total savings can end up unchanged or lower. A high MPS is virtuous for the individual but contractionary in aggregate during a slump, which is the Keynesian case for government spending when private demand collapses.
How is MPC measured in practice?
From household survey and tax data linking income changes to spending changes, often around stimulus payments or tax rebates which act as natural experiments. Estimates cluster around 0.5 to 0.9 depending on population and timeframe, with spending front-loaded in the first quarters after the income arrives.
Does MPC change over the business cycle?
Yes. In recessions, uncertainty pushes precautionary saving up and MPC down for middle earners, while stimulus still finds high MPC among the constrained. In booms, confidence lifts MPC. The parameter is behavioral, not physical, so it moves with sentiment and balance sheets.