MPS Calculator

How to use this MPS calculator

What this calculator does

This calculator estimates the marginal propensity to save, or MPS: the fraction of an increase in disposable income that is saved rather than consumed. It is a compact macroeconomics ratio, not a personal savings recommendation or a forecast of future household behavior. The calculation assumes the two amounts describe the same group, the same period, and the same currency. For background on the denominator, the U.S. Bureau of Economic Analysis defines disposable personal income as income available after current taxes.

When to use it

Use MPS when comparing how much of an income change is saved across two periods, when checking a macroeconomics exercise about saving and consumption, when translating a savings response into the complementary marginal propensity to consume, or when testing how a hypothetical change in household saving behavior affects the basic spend-versus-save split.

How to calculate

1. The calculator opens with a ready-to-use demonstration: a $1,000.00 increase in disposable income and a $300.00 increase in consumer savings. Its example workbook is available immediately.
2. Replace Increase in disposable income with the relevant positive change in after-tax income. Replace Increase in consumer savings with the amount saved from that change.
3. Read Marginal propensity to save (MPS) as a decimal ratio and Saved share as the same result in percentage form. Review Implied MPC, Implied consumption increase, and Saved per $1 of added income for complementary interpretations.
4. Select Download Excel to export the current validated inputs and results to an XLSX workbook. Reset clears the demonstration and all calculated content; after Reset, Excel export stays unavailable until both required fields form a complete valid state again.

Input guide

Increase in disposable income is required and must be a positive numeric amount. The control uses U.S.-style decimal notation, so values such as 1,000.00 are accepted while decimal-comma input such as 1,5 is rejected as ambiguous. Enter the change, not the household's total income. A larger denominator lowers MPS if the savings increase is held constant.

Increase in consumer savings is also required. Enter zero or a positive amount no greater than the disposable-income increase; for example, 300.00. A larger savings increase raises MPS. A common mistake is mixing a stock of existing savings with the change in savings caused by the income change. The calculator uses the change in savings, not the account balance.

Output guide

Marginal propensity to save (MPS) is the exact ratio Δs ÷ Δyd, shown here to three decimals. Saved share is that same ratio expressed as a percentage. Zero means none of the additional disposable income is saved; one means all of it is saved in this simplified model. Implied MPC is 1 – MPS, so lower MPS implies higher marginal consumption under the standard two-way identity. Implied consumption increase is the disposable-income increase minus the savings increase, expressed in dollars. Saved per $1 of added income translates MPS into a dollar-per-dollar reading.

The Calculation detail table repeats the two inputs, the implied consumption increase, MPS, and implied MPC using the same canonical calculation. The Measure column names each quantity, Value shows its formatted result, and Meaning gives the interpretation. These rows are explanatory identities rather than a forecast.

Worked example

With the startup values, disposable income rises by $1,000.00 and consumer savings rises by $300.00. The calculator divides 300 by 1,000 to obtain MPS = 0.300, equivalent to a 30.00% saved share. The complementary Implied MPC is 1 – 0.300 = 0.700. The implied consumption increase is $1,000.00 – $300.00 = $700.00, and the household saves $0.30 of each additional $1.00 of disposable income.

Learn more

The BEA explains that the broader personal saving rate measures saving relative to disposable income. That aggregate saving rate is not identical to MPS: a saving rate compares levels, while MPS focuses on changes. For macroeconomic context on why higher saving can have different short-run and long-run implications, the Federal Reserve Bank of St. Louis discusses the paradox of thrift and the spending-saving tradeoff.