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Logarithmic Price Scale


A logarithmic price scale, also known as a semi-log scale, is a type of scale used on a chart that displays price in a proportional manner. Instead of a standard linear progression where equal distance represents equal value change, each unit of movement on the vertical axis represents a percentage change in the underlying asset’s value. It’s frequently used in long-term investing charts to reflect the relative percentage change.


The phonetics of “Logarithmic Price Scale” is: loʊ-gəˈrɪθ-mɪk praɪs skeɪl.

Key Takeaways

  1. Measure Percentage Changes: Unlike linear price scales, a logarithmic price scale isn’t based on absolute price changes, but on the percentage change of an asset. This means they provide a more accurate picture of the asset’s historical price changes. Price increases and decreases of the same percentage are represented by the same vertical distance on the chart.
  2. Better For Long Term Analysis: The logarithmic price scale is more useful for long-term charts and analysis, where massive price changes occur over time. They can help to visualize asset performance over time better by showing significant price movements as equal distances despite the actual dollar amount changing.
  3. Effectiveness on Volatile Markets: Logarithmic price scales can be particularly effective while analyzing volatile markets. The percentage change viewpoint can provide a more accurate and detailed depiction of price movements for such assets, which helps traders and investors make more informed decisions about entry and exit points.


The Logarithmic Price Scale, also known as “log scale,” is a crucial tool used in business or finance, particularly in technical analysis while studying behavior and trends of financial markets. The significance of using a logarithmic scale over a linear scale comes from its ability to depict percentage changes or returns, rather than absolute changes. Therefore, the move from $10 to $20 is considered the same as the move from $20 to $40 as both represent a 100% gain. This is particularly useful for long-term charts, diversified portfolios, and volatile markets where exponential growth or decay are often observed. Hence, the log scale gives a more accurate picture of the investment’s relative performance over time, leading to more informed investment decisions.


A logarithmic price scale, or log scale, is predominantly used in finance and business to accurately represent the percentage changes in the value of a financial instrument like stocks, bonds or market indices. This is critical as it helps investors visualize relative changes or the rate of return on their investments over time, which in turn influences their investment strategies. For instance, on a log scale, a movement from $10 to $20 would appear the same as a movement from $20 to $40, which denotes the same 100% increase in both cases.The log scale is particularly useful when dealing with financial instruments that have exhibited high growth rates or substantial price changes. It helps accurately depict these variations and allows for better comparison across different time periods. Importantly, it also provides a clearer image of large value changes over time, that linear price scales may struggle to represent. Use of a log scale thus makes it easier for investors to interpret longer-term historical price data and facilitates the transfer of patterns and trends across different time scales. This ultimately supports investors when assessing risk and return, and in making better-informed investment decisions.


1. Stock Market Charts: An investor studying stock prices for companies like Apple, Google, or Amazon over a spot of ten years may use logarithmic price scales. These charts show percentage changes in stock prices rather than absolute changes over time. This helps the investor to understand long-term trends and volatility in the stock market.2. Forex Trading: Foreign exchange traders often use logarithmic price scales to examine the percentage change in currency exchange rates, rather than just the raw value. For instance, if a trader were studying the exchange rate trend of the US dollar to the Euro over a certain period of time, a logarithmic scale would allow them to see the rate of change more clearly.3. Index Fund Analysis: Logarithmic price scale can also be used to analyze the performance of index funds like S&P 500 or NASDAQ Composite. For example, if an investor was looking at the long-term performance of the S&P 500, using a logarithmic scale could show the data more understandably because it emphasizes the relative – not absolute – changes and trends. It would help to analyze larger data sets over a prolonged period more effectively.

Frequently Asked Questions(FAQ)

What is a Logarithmic Price Scale?

A logarithmic price scale is a type of scale used on a chart that depicts two equivalent price changes by the same vertical distance on the scale, regardless of what price level the asset is at when the change happens. It is also known as a log scale.

How does a Logarithmic Price Scale differ from a Linear Price Scale?

The key difference between a logarithmic price scale and a linear price scale reflects the price changes. In a linear price scale, price changes are represented by an equal vertical distance on the scale, regardless of the percentage change in price. However, a logarithmic price scale shows price changes as equal vertical distances but the changes refer to a relative or percentage change.

When should a Logarithmic Price scale be used?

Traders and investors often use logarithmic price scales when analyzing long-term charts and trends, as this can help them to understand proportionate increases and decreases better. It’s also often useful in volatile markets or when a particular asset’s price has experienced significant movements.

Can I use both Logarithmic Price Scale and Linear Price Scale?

Absolutely, both scales are used by traders and it often depends on personal preference when it comes to choosing which to use. Some may prefer a linear scale for its simplicity when identifying absolute changes, while others may prefer a logarithmic scale to analyze percentage changes.

What are the advantages of using a Logarithmic Price Scale?

Some of the benefits of a logarithmic price scale include a better visual impression of historical price performance and relative price changes. They can help to emphasize the percentage change, which can be more helpful in understanding a stock’s growth or decline over time.

Are there any disadvantages of using a Logarithmic Price Scale?

One potential downside to using a logarithmic price scale is that it can be slightly more complicated to read than a linear scale, especially for those who are new to chart analysis. Additionally, for short-term analysis or assets that have small price movements, a linear scale might be more useful.

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