---
name: "blkcalc"
section: "1"
platform: "linux"
package: "sleuthkit"
version: "4.15.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/blkcalc"
---

# blkcalc(1)

Converts between unallocated disk unit numbers and regular disk unit numbers.

## NAME

blkcalc - Converts between unallocated disk unit numbers and regular disk unit numbers.

## SYNOPSIS

**blkcalc \[-dsu unit\_addr\] \[-vV\] \[-i imgtype\] \[-o imgoffset\] \[-b dev\_sector\_size\] \[-f fstype\] image \[images\]**

## DESCRIPTION

**blkcalc** creates a disk unit number mapping between two images, one normal and  another that only contains the unallocated units of the first (the default behavior of the  **[blkls(1)](/blkls/1.md)** program).  One of the  **-d, -s,** or  **-u** options must be given.  If the  **-d** option is given, then the **unit\_addr** value is the disk unit address in the regular image (i.e. from  **dd** ). If the unit is unallocated, its address in an unallocated image is given.  If the  **-u** option is given, then the  **unit\_addr** value is the disk unit address in the unallocated unit image (i.e.  from  **[blkls(1)](/blkls/1.md)** ).  Its disk unit address in the original image is determined.  If the  **-s** option is given, then the **unit\_addr** value is the disk unit address in the slack image (i.e. from blkls -s). The **image** is the full, original image (i.e. from dd). **blkcalc** was called  **dcalc** in TSK versions prior to 3.0.0.

- \-f fstype

  Identify the File System type of the image. Use '-f list' to list the supported file system types. If not given, autodetection methods are used.

- \-i imgtype

  Identify the type of image file, such as raw. Use '-i list' to list the supported types. If not given, autodetection methods are used.

- \-o imgoffset

  The sector offset where the file system starts in the image.

- \-b dev\_sector\_size

  The size, in bytes, of the underlying device sectors.  If not given, the value in the image format is used (if it exists) or 512-bytes is assumed.

- \-v

  Verbose output to STDERR.

- \-V

  Display version.

- image \[images\]

  The disk or partition image to read, whose format is given with '-i'. Multiple image file names can be given if the image is split into multiple segments. If only one image file is given, and its name is the first in a sequence (e.g., as indicated by ending in '.001'), subsequent image segments will be included automatically.

This is useful when  keyword searching an image generated by **blkls.** This allows one to identify the original unit address and provides  better documentation.

## EXAMPLE

\# blkcalc -u 64 images/wd0e

## SEE ALSO

[**blkls**(1)](/blkls/1.md),

## AUTHOR

Brian Carrier \<carrier at sleuthkit dot org\>

Send documentation updates to \<doc-updates at sleuthkit dot org\>