inscape's preferences
I won't go into a huge tutorial on how to set up all Inkscape's preferences. But there is a feature I believe regular users may benefit from, particularly those who might consider using Inkscape with customers. This tweak will let you see items on screen you've drawn at the size they'd appear in print.

To access Inkscape's settings panel from the menu bar, click File > Inkscape Preferences.... From the keyboard: Shift + Ctrl + D.

The Inkscape Preferences may pop out on the right side of the application. If so, I recommend grabbing its title bar and dragging it away from the right side to make it free-floating.

Once detached, expand its size by clicking and dragging its edges outward. We'll need some significant space to perform the task at hand.

On the left side of the Inkscape Preferences panel is the word "Tools". Scroll down on that side until you see "Interface". Click that word. This is the area we'll be working on.

You should see a ruler to the right of "Zoom correction factor (in %):", so keep stretching the Inkscape Preferences box until you see a good bit of ruler. To the right of the ruler should be visible a drop-down box with a choice of measurements:

cm
ft
in
m
mm
pc
pt
px

I recommend using either cm or in.

Now find a ruler that matches the measurement system you chose (inches, centimetres) and bring it up the monitor. Adjust the number above the drop-down box until you have a close match. Fine tune it by adding decimal points. Example: my Samsung SyncMaster 206BW (1680 × 1080) prefers 109.50 for an exact match.

Once set, close the box and restart Inkscape.

Get a piece of printer paper (8½ × 11 paper or A4). Set the zoom to 1:1 (from the menu: View > Zoom > Zoom 1:1, from the keyboard: 1) on a blank document. Now compare the paper size to blank document on screen (don't touch it if you're using an older cathode ray tube - nasty things might happen). At this zoom the document on the screen should match your paper size pretty much exactly. No printing required for a basic view of the size of an item.

Comments welcome

BobSongs wrote:This tweak will let you see items on screen you've drawn at the size they'd appear in print.

It might be important to mention that this does not change Inkscape's internal resolution or the zoom factor in general: All it does is applying the correction factor to the preset zoom levels (accessible on the controls bar of the zoom tool and via keyboard shortcuts).

You can easily verify this by zooming '1:1' (e.g. by using the keyboard shortcut '1') after having set the zoom correction factor to match the current monitor resolution: the zoom factor displayed in the lower right corner of Inkscape's main window isn't 100% anymore, but 'zoom level 1:1' * 'zoom correction factor' -- using the zoom correction factor as set in the preferences.

Zooming to arbitrary levels (using the zoom tool, mouse or keyboard shortcuts) is not affected by the preference setting.

Related: The zoom correction factor was implemented as fix for
Bug #263989 in Inkscape: “Adjustment of displayed page size to match physical page size”