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.
In Photoshop CS6, 3D functionality is part of Photoshop Extended. All features in Photoshop Extended are part of Photoshop CC. Photoshop CC does not have a separate Extended offering.
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.
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.
Measurement scale is set automatically for DICOM files. See About DICOM files.
Choose Image > Analysis > Set Measurement Scale > Default to return to the default measurement scale, 1 pixel = 1 pixel.
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.
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.
Additional scale markers are placed in the same position on the image and can obscure each other, depending on their length. To view an underlying marker, turn off the scale marker layer set.
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.
Choose Image > Analysis > Set Measurement Scale and choose a measurement scale preset for the document (see Set the measurement scale), or choose Custom and set a custom measurement scale.
Choose Custom to select data points to measure.
Select an existing data point preset from the submenu.
In the Select Data Points dialog box, data points are grouped according to the measurement tool that can measure them. The Common data points are available for all tools. They add useful information to the Measurement Log such as the name of the file being measured, the measurement scale, and the date/time of the measurement.
By default all data points are selected. You can select a subset of data points for a particular type of measurement, then save the combination as a data point preset.
When you measure with a particular tool, only the data points associated with that tool are displayed in the log, even if other data points are selected. For example, if you make a measurement with the Ruler tool, only the Ruler tool data points appear in the Measurement Log, along with any Common data points that are selected.
- Choose an image feature and measurement tool to match the selected data points. Do one of the following:
Choose Image > Analysis > Record Measurements, or click Record Measurements in the Measurement Log panel.
If your currently selected data points do not correspond to the current measurement tool, you are asked to select data points for that tool.
The Measurement log has columns for each data point you selected in the Measurement Data Points dialog box. Each measurement you make enters a new row of data in the Measurement Log.
If you measure multiple selected areas on the image, one row of data is created in the log containing summary or cumulative data for all selected areas, followed by a row of data for each selection area. Each selection area is listed as a separate Feature in the Label column of the log and assigned a unique number.
You can repeat steps 2 through 6 for a variety of different selections in the same or multiple documents. The Document column in the Measurement Log reflects the source of the measurement data.
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).
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.
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.
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.
Click a row in the log to select it.
To select multiple contiguous rows, click the first row and drag through additional rows, or click the first row and then Shift-click the last row.
To select noncontiguous rows, click the first row and then Ctrl-click (Windows) or Command-click (Mac) additional rows.
To select all rows, click Select All.
To deselect all rows, click Select None.
Click a column header.
To select contiguous columns, click a column header and drag through additional columns, or click the first column header and then Shift-click the last column header.
To select noncontiguous columns, click the first column header and then Ctrl-click (Windows) or Command-click (Mac) additional column headers.
Drag selected columns to reorder them in the log. The column position is indicated by a double black line.
To resize a column, click the column header and then drag the separator.
To sort data in a column, click the column header to change the sort order, or right-click the header and choose Sort Ascending or Sort Descending. (Rows cannot be manually reordered.)
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.