Logarithmic versus percentage price scales: what the image means

A logarithmic price scale gives equal vertical space to equal price ratios: 50 to 100 occupies the same distance as 100 to 200. A linear percentage scale instead labels change from a reference value. These settings are not interchangeable. Before reviewing a screenshot, identify both what the axis labels measure and how the chart spaces those values.

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Separate spacing from the labels

With an ordinary linear price scale, the distance between 50 and 100 matches the distance between 100 and 150: both represent 50 price units. With a logarithmic scale, equal proportional changes occupy equal distances. StockCharts explains this distinction using repeated price doublings.

A log chart can still show ordinary price numbers on its axis. Seeing 50, 100 and 200 does not make it a linear chart; inspect their spacing and confirm the selected setting. The word “logarithmic” describes how values are positioned, not a requirement that the labels display percentages.

A percentage view needs another piece of information: the value used as its reference. TradingView's Supercharts settings guide describes Percent as a linear scale relative to the chart's starting point. A label of +20% therefore describes a change from that reference, not an absolute market price.

Follow one fictional sequence through the settings

This is an invented arithmetic exercise, not a market forecast or an actual ChartPilot result. Suppose three successive observations have prices of 50, 100 and 200, all in the same quote currency. Set the percentage reference to 50 and keep it fixed throughout this example.

The percentage calculation is (price ÷ reference − 1) × 100. Applying it gives:

The second and third observations each double the preceding price. A log price chart gives those two moves equal height. A linear percentage chart referenced to 50 moves first from 0% to +100%, then from +100% to +300%. Its second segment covers 200 percentage points, twice the first segment's 100 percentage points.

There is no contradiction. “Up 100% from the previous observation” and “up 300% from the original reference” use different denominators. The chart still contains the same prices. Changing the display did not change the observations or establish a trading opportunity.

Find what 0% refers to

Do not assume the zero reference is yesterday's close, your entry price or the first date you personally care about. Check the platform's setting and documentation. For example, TradingView's Lightweight Charts library defines Percentage mode relative to the first visible value, which becomes 0%. That is a documented rule for that library, not a promise about every charting product.

In a view that recalculates from the first visible value, moving the visible start can change the percentage labels. In our fictional sequence, if 100 becomes the new reference, the observation at 200 becomes +100% rather than +300%. A different reference explains the different label; no historical price needed to change.

Write the reference price and date in your own review notes. If you cannot establish them, mark the baseline unknown and return to absolute prices before comparing levels. A cropped image showing +20% and +30% alone does not identify the corresponding prices.

Prepare an image whose levels can be checked

1. Identify the chart. Retain the full symbol, provider, quote currency and timeframe. Confirm which axis belongs to the main price series if there are overlays.
2. Confirm the scale mode. Record whether it is regular price, log price or a percentage view. Do not infer the setting from a steep-looking line.
3. Preserve absolute values. For a review that discusses entry, stop or target prices, use a clear price view with several readable axis labels. A single last-price badge does not make all earlier percentage levels self-explanatory.
4. Keep the relevant context. Show the earlier swings behind your question as well as the latest candles. If changing settings changes the framing, inspect the final image again.
5. Recheck annotations. Read a drawn level against the numeric axis. Avoid estimating an intermediate price by evenly dividing pixels on a logarithmic scale.

As another mathematical check, the vertical midpoint between 100 and 400 on a log scale is 200, because both halves represent a doubling. On a linear price scale it is 250. Guessing the midpoint from an unlabeled image can therefore assign the wrong price even when the picture is sharp.

The general screenshot checklist covers capture quality and privacy. For a currency-specific unit check, see GBPUSD price digits and pip distances.

Check the assessment against numbers, not visual height

Upload a readable JPG, PNG or WebP image. ChartPilot provides a BUY or SELL outlook, reference levels and confidence in the visible evidence for readable supported charts. Compare any reported level with the source chart's actual price labels. Confidence is not a win probability, and AI can misread an axis.

If a report appears to treat a percentage label as a market price, do not repair the result by guessing. Return to the chart and capture a clearer absolute-price view. Then check how the reference entry, stop and target fit together. A screenshot assessment neither supplies a live quote nor executes a trade.

Review current signup options when your image passes the axis check. Keep three facts alongside the review: the scale setting, any percentage reference, and the absolute prices behind the levels you discuss.