An ordinary volume chart puts volume under time. A volume profile puts it beside price. The question changes from "when did people trade?" to "at what prices did they trade?"
About the Numbers in This Tutorial
Every figure below comes from one SPY reading taken on 21 July 2026, carried through the whole tutorial as a single worked example. Open the tool today and your numbers will differ, because each profile window rolls forward, moving the POC and the value area with it. The reasoning is what transfers, not the readings.
Turning the chart on its side
The tool takes the window's full high-to-low range and slices it into 60 horizontal bins. Every session's volume is then poured into the bins its range covered, and the result is drawn as horizontal bars: long bars are prices where a lot of business happened, short bars are prices the market passed through quickly.
An ordinary volume chart runs along the bottom. A profile turns it sideways so it sits beside price.
Volume is spread, not dumped
A daily bar does not tell you where within its range the volume traded, so the tool makes the even assumption: each session's volume is distributed across the bins its high-to-low range touches, in proportion to how much of the range falls in each bin.
A session spanning three bins puts roughly a third of its volume in each; a quiet session inside a single bin puts all of it there. This is what keeps a wide-range day from being credited entirely to one price it barely visited.
It Is an Approximation
True volume-by-price needs intraday tick data. Built from daily bars, this is an estimate, and it assumes volume was spread evenly through each session's range. On a day that opened at one extreme and closed at the other, that assumption is doing real work. It is a good approximation, not a measurement.
Three things are pulled out of that histogram, and each is defined precisely.
Price runs up the side, volume runs across. The longest bar is the POC.
Point of control
The POC is simply the fullest bin: the single price at which more volume changed hands than any other in the window. It is the profile's center of gravity and the level most participants have a position around.
Value area
The value area is the band holding 70% of the window's volume. It is built by starting at the POC and expanding outward one bin at a time, always taking whichever neighbor holds more volume, until 70% is enclosed.
Because it grows toward the heavier side, the value area is rarely centered on the POC. It leans toward wherever the trading actually was.
Shelves
A shelf is a local peak in the profile that is also heavy in absolute terms: a bin holding more volume than both its neighbors and ranking in the top 30% of all bins. Both conditions have to hold, which stops a small bump in a quiet stretch from qualifying.
The tool then reports the nearest shelf below the current price as support and the nearest above it as resistance.
Chapter 3
The Window Changes the Answer
The only control on the page is the trailing window: 1M, 3M or 6M. It is not a refinement dial. It can hand you a completely different read on the same ticker.
SPY, one afternoon, three windows
Window
POC
Value area
Width
1M (21 sessions)
$748.75
$739.33 – $754.28
$14.95
3M (63 sessions)
$748.29
$732.31 – $755.56
$23.25
6M (126 sessions)
$682.82
$633.65 – $731.99
$98.34
Measured on SPY, 21 July 2026, with the price at $748.28.
Read what happened between the rows
On the 1M and 3M profiles, SPY was sitting almost exactly on its POC. Price, the busiest level, and the nearest resistance shelf were all within pennies of each other. The reading is "the market is at fair value and has been trading here".
Switch to 6M and the same instant looks nothing alike. The POC drops to $682.82, roughly 9.6% below the current price, and the value area tops out at $731.99. Price is not near the middle of that profile; it is outside it entirely, above the value area high.
Both readings are correct. Over one month SPY has been trading here. Over six months it has spent most of its volume far lower and has recently left that zone behind. Those are different facts, and which one matters depends entirely on the horizon you care about.
The Rule This Suggests
Check more than one window before drawing a conclusion. If the POC barely moves between them, the level is well established. If it jumps as it does here, the ticker has repriced and the shorter and longer profiles are describing different regimes.
Longer windows widen everything
The value area goes from about $15 wide at one month to $98 at six. That is not a change in method, only in how much ground price covered. A wide value area is less useful as a boundary, because "inside the value area" stops being a meaningful constraint once it spans 13% of the price.
Point of Control, the most-traded price in the window.
Nearest Support Shelf, the closest heavy level below the current price, with the distance in percent.
Nearest Resistance Shelf, the same above. Either can read None when no qualifying shelf exists on that side, which is itself informative: nothing standing between price and open air.
Value Area, the band holding 70% of the volume.
The distances are given in percent rather than dollars, which is what makes them portable between tickers.
The profile
Each horizontal bar is one of the 60 bins, its length the volume traded there. Bar shading ramps with intensity so the heavy levels stand out, the POC is drawn in full brand color and tagged with its price, and shelves are always rendered strongly enough to read even when the surrounding bins are faint.
Hovering any bar gives the exact volume at that level and labels it if it is the POC or a shelf. That is the fastest way to check whether a shelf is a towering level or merely the tallest bar in a quiet neighborhood.
Reading Tip
Look at the shape before the numbers. A profile with one dominant peak describes a market that agreed on a price. A profile with two widely separated peaks describes two regimes stitched together, and its POC sits in a valley between them where comparatively little actually traded.
Chapter 5
How Traders Use It
Five uses, each tied to a specific reading on the page.
1. Levels that come from participation
A shelf is support or resistance for a concrete reason: a lot of people transacted there, so a lot of positions have that price as their reference. Returning to it brings out the people who wish they had done something different, and that supply or demand is what slows the move. It is a level with a mechanism behind it rather than a line drawn on a chart.
2. The POC as a magnet
Price that drifts away from the busiest level often comes back to it, simply because that is where the most willing counterparties are. The POC is the profile's center of gravity, and distance from it is a rough measure of how far the market has wandered from consensus.
3. Value-area position
Inside the value area is the market agreeing with itself. Outside it, as SPY was on the 6-month profile, is the market having moved somewhere it has not yet done much business. That state resolves one of two ways: price builds a new shelf at the higher level, or falls back into the old area.
4. Empty space as a fast lane
The short bars matter as much as the long ones. A stretch of thin bins is a price range the market moved through quickly and left no positions in, so there is little to slow a move that re-enters it. Gaps in a profile are where price tends to travel fastest.
5. Context for a breakout
A break above a heavy shelf is a different event from a break through thin air. The first cleared real supply; the second cleared nothing and can reverse just as easily. Checking what sits immediately above a level before it breaks is one of the more practical uses of the whole page.
Combining Windows
The strongest levels are the ones that survive a change of window. A shelf that appears at 1M, 3M and 6M has been heavily traded on every timescale. One that only exists at 6M is old business that recent trading has moved on from.
The tool has its own guided walkthrough if you want the parts pointed out on the live page: