Output gap calculator
Compare actual output with potential output and read the gap as a percent of potential, plus the absolute difference in levels. Or start from a gap percent and solve for the missing level. This is the standard classroom definition. It is not an official estimate, not a forecast, and not investment advice. The arithmetic runs entirely in your browser.
Mode
Percent of potential uses actual output Y and potential output Y*. The gap in percent is ((Y minus Y*) divided by Y*) times 100. From levels uses the same two inputs and also reports the absolute gap, Y minus Y*.
The activity level you want to compare. An index such as 102 works. A GDP level works too, if potential uses the same units. Type the number yourself. This page does not download a BEA, ONS, or CBO series.
The sustainable benchmark. Potential output is an estimate, not a shop receipt. Use the same units as actual output. The percent gap divides by this number, so zero does not work.
Known actual output. The calculator solves for the potential level that would produce the gap percent below.
Positive means actual output sits above potential. Example: 2 with actual output of 102 solves for potential of 100.
Known potential output. The calculator solves for the actual level that would produce the gap percent below.
Positive means actual output sits above potential. Example: 2 with potential of 100 solves for actual output of 102.
Output gap (%)
Absolute gap
How to read this
Arithmetic
Defaults use actual output of 102 and potential output of 100. The output gap is plus 2 percent of potential. The absolute gap is plus 2 in the same units. Switch to implied potential, keep actual output at 102, and enter a gap of 2 percent. Potential comes back to 100. Switch to implied actual, keep potential at 100, and enter a gap of 2 percent. Actual output comes back to 102. Those figures are classroom arithmetic. They are not a claim about current GDP.
Not investment advice and not policy advice. Nothing here recommends buying, selling, or holding any security, or choosing a tax, spending, or interest rate. A positive gap is not a signal to trade. A negative gap is not a forecast of the next GDP release. The calculator does not fetch live data and does not invent an official series.
The classroom formula
This page uses the percent of potential definition common in textbooks and in public discussions of the gap:
Output gap (%) ≈ ((Y − Y*) / Y*) × 100
Absolute gap ≈ Y − Y*
Y* ≈ Y / (1 + output gap as a decimal)
Y ≈ Y* × (1 + output gap as a decimal)
Y is actual output. Y* is potential output. A gap of 2 percent has decimal form 0.02, so potential equals actual divided by 1.02, and actual equals potential times 1.02. Say which levels you used. Potential is an assumption you type, or a published estimate you have already read, not a fact this page looks up.
For the ideas and the loose spots, read the output gap. The same percent is an input on the Taylor rule calculator. A related sketch, Okun's law, links a GDP growth gap to unemployment. Try the Okun's law calculator. The Phillips curve calculator uses an unemployment gap, which is a different object from this output gap.
Where to find the inputs
Type your own numbers. This page does not download official series. For a US sketch, look up real GDP at BEA and a potential GDP discussion at the Congressional Budget Office. FRED charts a real potential GDP series under GDPPOT next to BEA real GDP. For a UK sketch, look up real GDP at ONS. The Office for Budget Responsibility discusses potential output and the output gap, and treats a negative gap as spare capacity. The Bank of England discusses spare capacity in its Monetary Policy Report. Those publications are estimates with methods attached. Copy a figure only after you have read the notes, then type it here. Broader context sits on the GDP pillar and the unemployment pillar.
UK and US framing
Do not paste a US potential series onto UK data and call the result a fact. CBO potential GDP is built for the US national accounts. UK spare capacity talk from the OBR and the Bank of England uses different models, different price concepts, and a different policy horizon. The OBR has noted that its output gap and the Bank’s slack measure are not the same object, because the time horizon differs. A 2 percent gap next to an index of 100 is classroom arithmetic. A 2 percent gap in a published chart is an estimate that can be revised. Match the units before you type.
Sources
- Congressional Budget Office, “Why CBO Projects That Actual Output Will Be Below Potential Output on Average”
- Congressional Budget Office, “Additional Information About the Economic Outlook: 2021 to 2031” (defines the output gap as GDP minus potential GDP, as a percentage of potential GDP)
- FRED, Real Potential Gross Domestic Product (GDPPOT)
- BEA, Gross Domestic Product
- Office for Budget Responsibility, Potential output and the output gap
- Office for Budget Responsibility, Spare capacity in the February 2014 Inflation Report (why the OBR output gap and Bank of England slack are not the same object)
- Bank of England, Monetary Policy Report, February 2026 (spare capacity discussion)
- ONS, Gross Domestic Product (GDP)
- Sarwat Jahan and Ahmed Saber Mahmud, “The Output Gap: Veering from Potential,” IMF Finance and Development, Back to Basics
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