Measurement

Using the Photoshop Measurement feature you can measure any area defined with the Ruler tool or with a selection tool, including irregular areas selected with the Lasso, Quick Select, or Magic Wand tools. You can also compute the height, width, area, and perimeter, or track measurements of one image or multiple images. Measurement data is recorded in the Measurement Log panel. You can customize the Measurement Log columns, sort data within columns, and export data from the log to a tab-delimited, Unicode text file.

Measurement scale

Setting a measurement scale sets a specified number of pixels in the image equal to a number of scale units, such as inches, millimeters, or microns. Once you’ve created a scale, you can measure areas and receive calculations and log results in the selected scale units. You can create multiple measurement scale presets, although only one scale can be used in a document at a time.

Scale markers

You can place scale markers on an image to display the measurement scale. Scale markers can appear with or without a caption displaying measurement scale units.

Set the measurement scale

Use the Ruler tool to set the measurement scale for a document. You can create measurement scale presets for frequently used measurement scales. Presets are added to the Image > Analysis > Set Measurement Scale submenu. The current measurement scale for a document is checked in the submenu, and appears in the Info panel.

Choose Image > Analysis > Set Measurement Scale > Default to return to the default measurement scale, 1 pixel = 1 pixel.

Set measurement scale

Create a measurement scale preset

Delete a measurement scale preset

Use scale markers

Measurement scale markers display the measurement scale used in your document. Set the measurement scale for a document before creating a scale marker. You can set the marker length in logical units, include a text caption indicating the length, and set the marker and caption color to black or white.

Create a scale marker

The scale marker is placed in the lower left corner of the image. The marker adds a layer group to the document, containing a text layer (if the Display Text option is selected) and a graphic layer. You can use the Move tool to move the scale marker, or the Text tool to edit the caption or change text size, font, or color.

Add or replace scale markers

You can place multiple scale markers in a document, or replace existing markers.

Delete a scale marker

Perform a measurement

You can measure using the Photoshop selection tools, Ruler tool, or Count tool. Choose a measurement tool that matches the type of data you want to record in the Measurement Log.

• Create a selection area to measure values such as height, width, perimeter, area, and pixel gray values. You can measure one selection or several selections at once.

• Draw a line with the Ruler tool to measure linear distance and angle.

• Use the Count tool to count items on the image, then record the number of items. See Counting objects in an image.

  Each measurement measures one or more data points. The data points you select determine the information recorded in the Measurement Log. Data points correspond to the type of tool you’re measuring with. Area, perimeter, height, and width are available data points for measuring selections. Length and angle are available data points for Ruler tool measurements. You can create and save sets of data points for particular types of measurements to speed your workflow.

Measurement data points

Angle of orientation (±0‑180) of the Ruler tool.

Area of selection in square pixels, or in calibrated units according to the current measurement scale (such as square millimeters).

4pi(area/perimeter²). A value of 1.0 indicates a perfect circle. As the value approaches 0.0, it indicates an increasingly elongated polygon. Values may not be valid for very small selections.

Varies according to the measuring tool used. Selection tool: the number of discontiguous selection areas on the image. Count tool: the number of counted items on the image. Ruler tool: the number of Ruler lines visible (1 or 2).

Applies a date/time stamp of when the measurement occurred.

Identifies the document (file) measured.

This is a measurement of brightness, either from 0 to 255 (for 8‑bit images), 0 to 32,768 (for 16‑bit images), or 0.0 to 10 (for 32‑bit images). For all gray value-related measurements, the image is internally converted to grayscale (equivalent to choosing Image > Mode > Grayscale) using the default grayscale profile. Then the requested calculations (mean, median, minimum, maximum) are calculated for each feature and for the summary.

Height of the selection (max y - min y), in units according to the current measurement scale.

Generates histogram data for each channel in the image (three for RGB images, four for CMYK, and so on), recording the number of pixels at each value from 0 to 255 (16‑bit or 32‑bit values are converted to 8‑bit). When you export data from the Measurement Log, the numeric histogram data is exported to a CSV (comma-separated value) file. The file is placed in its own folder at the same location where the measurement log tab-delimited text file is exported. Histogram files are assigned a unique number, starting at 0, and progressing by 1. For multiple selections measured at once, one histogram file is generated for the total selected area, plus additional histogram files for each selection.

The sum of the values of the pixels in the selection. This is equivalent to the product of Area (in pixels) and Mean Gray Value.

Identifies and automatically numbers each measurement as Measurement 1, Measurement 2, and so on. For multiple selections measured simultaneously, each selection is assigned an additional Feature label and number.

Linear distance defined by the Ruler tool on the image, in units according to the current measurement scale.

The perimeter of the selection. For multiple selections measured at once, one measurement is generated for the total perimeter of all selections, plus additional measurements for each selection.

The measurement scale of the source document (for example, 100 px = 3 miles).

Logical units of the measurement scale.

The number of pixels assigned to the scale unit.

Source of the measurement: Ruler tool, Count tool, or Selection.

Width of the selection (max x - min x), in units according to the current measurement scale.

Create a data point preset

Edit a data point preset

Delete a data point preset

Use the Measurement Log

When you measure an object, the Measurement Log panel records the measurement data. Each row in the log represents a measurement set; columns represent the data points in a measurement set.

When you measure an object, a new row appears in the Measurement Log. You can reorder columns in the log, sort data in columns, delete rows or columns, or export data from the log to a comma-delimited text file.

Display the Measurement Log

Select rows in the log

Select columns in the log

Reorder, resize, or sort columns in the log

Delete rows or columns from the log

Export Measurement Log data

You can export data from the Measurement Log into a comma-delimited text file. You can open the text file in a spreadsheet application and perform statistical or analytical calculations from the measurement data.