What does Bollinger Bands percent B measure?

Bollinger Bands percent B measures where the chosen price sits relative to its bands. With nonzero symmetric bands, 0 is the lower band, 0.5 is the basis, and 1 is the upper band. It does not measure the probability of reversal.

Can Bollinger %B be negative or greater than 1?

Yes. With lower 90 and upper 110, a price of 85 produces -0.25 and a price of 115 produces 1.25. Both are valid formula results. A script that clips them to the 0-to-1 range loses information about prices outside the bands.

What happens when the upper and lower bands are equal?

The %B denominator becomes zero, so the ratio is undefined. If all three inputs equal 100, the result is 0/0. This page specifies na and no threshold event for that case. Substituting 0 or 0.5 would invent a price location.

Is 0.8 the same as 80% for Bollinger %B?

Yes, if the percentage display is the decimal ratio multiplied by 100. It means price is 80% of the way from the lower band to the upper band. It is not an 80% gain, an 80% chance of success, or a BandWidth reading.

Why does a custom %B script differ from TradingView?

First compare the source, length, multiplier, band formula, symbol, and timeframe. Then inspect the same closed bar with unrounded inputs. A percent-scaled plot differs by a factor of 100 from a decimal plot; missing-value handling and open-bar updates can also explain differences.

Does a %B value above 1 mean sell?

A value above 1 only locates price above the upper band. John Bollinger warns that band tags alone are not trading signals, and prices can follow an outer band during a trend. A testable strategy still needs its own entry, exit, risk, and cost rules.

Bollinger Bands %B on TradingView

Bollinger percent B indicator: formula and limits

The Bollinger percent B indicator measures price location relative to the lower and upper Bollinger Bands. Its decimal value is 0 at the lower band, 0.5 at the middle band, and 1 at the upper band when the bands are symmetric and have nonzero width.

Generate the %B script Calculate the bands

Direct answer

%B = (price - lower band) / (upper band - lower band). Values below 0 or above 1 are valid positions outside the bands. When the bands coincide, the denominator is zero and the ratio is undefined; it is not a neutral reading of 0.5.

Starting values

Lower band

%B = 0

Middle band

%B = 0.5

Upper band

%B = 1

Zero band width

Undefined ratio

Checks before using the result

1
Match the price source, length, deviation multiplier, symbol, and timeframe before comparing two %B series.
2
Keep thresholds on the same scale: decimal 0.8 equals 80% of the distance from the lower to the upper band.
3
Check missing and zero-width values separately. Replacing an undefined value with 0 would falsely place price at the lower band.

Calculate position from the same bar

Use price and both band values from the same bar. TradingView documents close, length 20, and a deviation multiplier of 2 as defaults. Record any changes to those inputs before comparing results.

Subtract the lower band from the selected price.
Divide by upper band minus lower band, provided that distance is positive.
Keep the unrounded result for conditions; round only the displayed value.

Worked example: lower 90, upper 110

This hypothetical arithmetic example holds the bands fixed at 90 and 110. Their midpoint is 100 and their distance is 20. At price 105, %B = (105 - 90) / 20 = 0.75. These are independent input snapshots, not successive bars or measured market results. The table below checks the same formula at each price.

Price 85 gives (85 - 90) / 20 = -0.25: 5 units below the lower band.
Price 115 gives (115 - 90) / 20 = 1.25: 5 units above the upper band.
Do not clamp either result to 0 or 1. Clamping would erase how far price moved outside the bands.

Handle zero width and missing inputs explicitly

If price, lower band, and upper band all equal 100, the formula becomes (100 - 100) / (100 - 100) = 0/0. It has no defined value. A flat price window can produce coincident bands; a zero deviation multiplier can also collapse them. This page specifies na for that case, rather than asserting an undocumented TradingView fallback.

Return na when either band or the price is missing, or when the band distance is not positive.
Skip threshold events until both the previous and current %B values are defined. A missing value is not a crossing.
A very small positive band distance is still valid, but the ratio is sensitive to tiny price changes. Inspect unrounded inputs before diagnosing a large value as a bug.

Decimal values and percentage displays

Multiplying decimal %B by 100 changes the display scale, not the price location. The worked value 0.75 becomes 75%, and 1.25 becomes 125%. Neither value describes an investment return or the probability of a price move. A threshold entered as 80 into a decimal series does not mean 80%; it means eighty full band distances from the lower band.

Compare closed bars in TradingView

Add Bollinger Bands %b to the chart and match its settings to the bands used in your calculation. Compare the Data Window values on one closed bar at a time. An open bar can change both price and the bands, so an intrabar threshold event can disappear before the close.

Start with a closed bar inside the bands, then inspect one outside them and any flat or missing-data cases available in the dataset.
Distinguish a level from a cross: 0.79 to 0.81 crosses above 0.8; 0.81 to 0.83 remains above it but does not cross again.
For chart-timeframe alerts, require a confirmed bar and configure delivery at bar close. Pine barstate.isconfirmed is true on historical bars and on the closing update of a realtime bar.

%B and BandWidth answer different questions

%B measures position; BandWidth measures the distance between the bands relative to their middle line. In a hypothetical symmetric example, price 100 gives %B = 0.5 with bands 90/110 and also with bands 99/101. The raw band distances are 20 and 2, despite identical %B. John Bollinger also cautions that touching a band alone does not supply a buy or sell signal. Price can remain near a band during a trend.

Hand-check %B with fixed bands of 90 and 110

Price and position	Decimal calculation	Percentage display
85: below lower	-5 / 20 = -0.25	-25%
90: at lower	0 / 20 = 0	0%
95: inside	5 / 20 = 0.25	25%
100: at midpoint	10 / 20 = 0.5	50%
105: inside	15 / 20 = 0.75	75%
110: at upper	20 / 20 = 1	100%
115: above upper	25 / 20 = 1.25	125%

Bollinger %B Pine Script prompt

Use the Pine Script AI Coding Agent to draft a checkable indicator from this specification. Verify the returned series bar by bar before defining strategy entries, exits, position sizing, and costs.

Create a Pine Script v6 Bollinger Bands %B indicator on the chart timeframe. Use close, a 20-bar SMA, and 2 standard deviations as defaults; expose source, length, and a positive multiplier. Calculate the decimal ratio of price minus lower band to upper band minus lower band. Return na for missing inputs or nonpositive band width, and never clamp valid results to 0 or 1. Plot decimal reference levels 0, 0.5, and 1. Add separate confirmed-bar alerts for crossing above 0.8, below 0.2, above 1, and below 0. Require valid previous and current values for crossing events. Expose the source and band values for Data Window inspection. Explain warm-up behavior and compare values against the hand calculation before adding any strategy orders.

Generate the %B script

Related Bollinger Bands pages

TradingView indicatorsBrowse indicator formulas, settings, and validation guides.Bollinger Bands calculatorCalculate the upper, middle, and lower values used by %B.Modified Bollinger BandsInspect Pine Script for a modified %B-style indicator.Bollinger BandWidthMeasure band width instead of price location.Bollinger Bands crossoverDefine the direction and confirmation of band crossings.

Sources and method notes

Bollinger Bands %bTradingView Help CenterDecimal formula, reference levels, and default inputs.Bollinger Bands rulesJohn BollingerRules 6, 7, 15, and 18 distinguish band tags, price position, and width.Percent B (%B)Fidelity Learning CenterPercentage-scale formula and interpretation.Bar statesTradingView Pine Script documentationThe timing of barstate.isconfirmed on historical and realtime bars.

Pineify provides tools and information, not investment advice. The numbers on this page are hypothetical calculations. %B does not guarantee a reversal, continuation, or return.