Logarithmic vs Linear: What Beginners Should Know

Logarithmic and linear in plain terms

A linear scale means equal steps on the axis represent equal steps in the underlying value (for example, equal price increments). A logarithmic scale (log scale) means equal steps represent equal relative changes—commonly equal percentage changes—so the chart spacing adapts to the current level.

Beginners often encounter these terms when comparing chart views. The key idea is not that one is “right,” but that each scale answers a different question:

Linear asks: “How much did the value change in absolute terms?”
Logarithmic asks: “How much did the value change in relative terms?”

Because visuals differ, a setup that looks like a “similar move” on one scale may not look similar on the other.

How the mechanics affect what you see

Both scales start from the same numeric data, but they transform the way that data is mapped to the vertical axis.

Linear mechanics

On a linear axis, if the price is 100 and then 110, that is a +10 absolute change. On the chart, a +10 move will occupy the same vertical distance regardless of whether the price was near 50 or near 200.

Logarithmic mechanics

On a log axis, equal spacing typically corresponds to equal relative change. For example, moving from 100 to 200 is a +100% change, and that kind of doubling can appear as the same vertical distance as another doubling, even if it happens at a different starting price.

Assumptions for examples

To verify these interpretations yourself, you need to assume:

The chart truly uses the scale type stated (linear vs log).
The axis mapping is based on the intended base (often discussed as base-10 or base-e, depending on software). Many platforms implement log scaling consistently within their charting system, but you should not assume the same base across tools.
You are comparing the same instrument and timeframe.

A concrete comparison you can verify

Assume a value moves from A to B.

Let A = 50.
Consider a second scenario where A = 100.

Now compare two moves that have the same percentage but different absolute sizes:

From 50 to 100: that is a +100% move and an absolute change of +50.
From 100 to 200: that is also a +100% move and an absolute change of +100.

On a log axis, these two +100% moves are often presented with similar spacing because they represent the same relative change. On a linear axis, the second move’s absolute change (+100) is twice the first’s (+50), so it will generally appear larger in distance.

This is a major practical limitation: if you measure “how far” something moved visually, you must understand whether the chart is using absolute or relative spacing.

Limitations and failure modes to watch

Overconfidence from visuals: A trend-like shape on one scale can become less convincing on the other. The chart transformation changes perception; it does not create new information.
Context mismatch: If you compare two charts with different scales (one linear, one log), you may misinterpret what looks “equivalent.” A move that is “equal in distance” may be equal in percentage on one view and equal in absolute value on the other.
Measurement errors from hidden assumptions: Beginners may perform calculations using absolute differences while the chart is interpreting relative differences (or vice versa). The fix is verification: state whether you are working with absolute changes or percentage changes.
Market and tooling factors not captured by scaling: Chart scaling alone does not account for execution costs, bid/ask spreads, liquidity changes, or jurisdiction-specific rules. Those factors can materially affect outcomes even when the chart transformation is applied correctly.
Historical relationships ≠ future behavior: Any repeated visual pattern in the past can fail in the future because market dynamics change. A scale affects representation; it cannot guarantee persistence.

Verification and next question for independent learning

To independently verify what you learn, do three checks:

Confirm the chart’s scale setting (linear vs log) and keep it consistent while you compare. 2) Pick a start price and compute the move as an absolute change and as a percentage change; then see which interpretation matches the spacing you observe.