Volume & money flowUp/Down Volume Ratio · UVDV
The ratio of volume transacted on up-closes to volume on down-closes — a direct read on accumulation versus distribution.
Works in most conditionsEngine-computed on a fixed sample series
What it is
The Up/Down Volume Ratio is a volume indicator that directly measures accumulation versus distribution by asking a blunt question: over a recent stretch, did more shares trade on days that closed up or on days that closed down? Popularized in the growth-stock world of William O'Neil and CAN SLIM investing, it is designed to reveal institutional demand, because big funds cannot buy meaningful positions without leaving a footprint of heavy up-day volume. Applied to a single stock it contrasts the participation on advancing days versus declining days; applied to a whole market index it uses advancing volume versus declining volume as a breadth gauge. The output is a simple ratio around the pivotal value of 1, and for a beginner it reads like a demand scoreboard: above 1 means buyers are showing up in force, below 1 means sellers are.
How it is calculated
Over a chosen lookback, commonly 50 days, the indicator sums the volume of every bar that closed higher than its prior close into an up-volume total, and separately sums the volume of every bar that closed lower into a down-volume total. The ratio is simply the up-volume total divided by the down-volume total. A value of exactly 1 means equal volume changed hands on up and down days; a value of 2 means twice as much volume traded on up days as down days. On a broad index the same logic uses the exchange's advancing volume and declining volume rather than a single instrument's up and down closes. There is no smoothing beyond the summation window, so the only real parameter is the lookback length, which controls how much history the ratio digests.
Reading it, step by step
Start with the 1.0 dividing line: a ratio above 1 signals net accumulation, meaning demand is outrunning supply, while a ratio below 1 signals net distribution. The magnitude matters as much as the side. A reading drifting between 1.0 and 1.5 is mildly positive, but a jump above roughly 2.0 marks aggressive, urgent buying, the signature O'Neil associated with leading stocks emerging from sound bases. On the downside, a ratio sinking toward 0.5 or below shows heavy selling and warns that a stock is under distribution. On an index, a persistently elevated up/down volume ratio confirms a healthy, broadly participated advance, whereas a market rising on a ratio near or below 1 is climbing on thin, suspect demand that may not last.
Best timeframes and settings
The classic setting is a 50-day lookback on daily charts, which aligns with the swing and position horizons of growth-stock investors screening for institutional demand. Fifty days is roughly ten trading weeks, long enough to capture the accumulation that builds through a base but short enough to stay current. Shortening the window toward 20 or 25 days makes the ratio more responsive to a recent surge of buying, which helps catch fresh demand early but makes the reading jumpier and more prone to being swayed by a single big day. Lengthening it toward 100 days smooths the signal for position traders who want a structural read on accumulation. It is primarily a daily-chart, longer-horizon tool and is not well suited to scalping, where single-session volume classification is too coarse to be useful.
When and where to use it
This ratio is most powerful during the basing and breakout phases of a stock's cycle, where the whole game is detecting whether institutions are quietly accumulating before a move. It is a staple in growth and momentum screening, used to filter for names showing demand that could power a sustained advance. As a market-breadth tool the index version helps you judge the health of a broad rally, distinguishing a well-supported bull leg from a narrow, fragile one. Avoid relying on it for instruments with unreliable or fragmented volume, and be cautious using it on very low-volume stocks where a few large trades distort the totals. It answers a demand-versus-supply question, so pair it with price structure rather than expecting it to call exact tops and bottoms.
Strategies that use it
The signature O'Neil-style strategy is a demand-confirmed breakout: as a stock finishes a proper base, screen for an up/down volume ratio that has climbed above 2.0, then buy the breakout above the base's pivot point, using the base low as your stop and trailing as the trend develops. A second strategy is a distribution exit filter: if you hold a winner and its up/down volume ratio deteriorates below 1.0, treat that as evidence institutions are unloading and tighten stops or reduce size. A third is a market-timing overlay: only take new long positions when the broad index's advancing-versus-declining volume ratio is healthy and above 1, standing aside when market-wide selling volume dominates. In each case the ratio confirms who is in control of participation, aligning your trades with institutional flow.
Combining it with other indicators
The Up/Down Volume Ratio works hand in glove with base and breakout price patterns, because the pattern defines the level and the ratio validates the demand behind it. Relative strength versus the broad market complements it in growth screening, so you buy strong stocks under accumulation rather than laggards. On-Balance Volume and the Accumulation-Distribution line add a cumulative view of the same buying pressure the ratio measures over a fixed window, and agreement across them strengthens the case. A moving average of price supplies trend context so you buy accumulation in uptrends rather than fighting a downtrend. Broad-market breadth measures such as the advance-decline line pair with the index version to confirm that a rally is genuinely well-supported.
Where it fails
The ratio's core weakness is that it smears an entire bar's volume onto the direction of the close, so a session that traded violently in both directions but happened to close marginally up is counted as pure buying, which misclassifies mixed action. Short lookbacks make it jumpy and easily dominated by one enormous volume day that may reflect an index rebalance or a one-off event rather than real demand. It depends on trustworthy volume, so on fragmented, synthetic, or thinly traded instruments the reading can mislead. The classic mistake is buying a high ratio in isolation without a valid base or breakout, chasing a number rather than a setup. Avoid these traps by using it as confirmation alongside price structure, by choosing a lookback long enough to dilute single-day distortions, and by trusting it only where volume data is reliable.
A worked example
Suppose a growth stock has spent eight weeks building a flat base and you compute its up/down volume ratio over the last 50 days. The up-volume total, summing every up-close day's volume, comes to 400 million shares, while the down-volume total comes to 180 million shares. The ratio is 400 divided by 180, roughly 2.2, comfortably above the 2.0 threshold that flags aggressive institutional demand. This tells you that even as the stock chopped sideways, far more volume was transacting on advancing days than declining ones, the fingerprint of quiet accumulation. When price then breaks above the base's pivot on a strong-volume day, you already have confirmation that demand is real, so you take the long with a stop just beneath the base and let the position run as the demand you detected plays out in price.