Rectangle on an Ultrawide Monitor: Making Thirds and Sixths Actually Useful
A standard 16:9 monitor rarely justifies more than two windows side by side — a third column usually ends up too narrow to use. An ultrawide changes that math. A 34″ 21:9 display (typically 3440×1440) or a 49″ 32:9 super-ultrawide (typically 5120×1440, effectively two 27″ 1440p screens stitched together) has enough logical width that thirds, sixths, and even a persistent narrow sidebar app all become genuinely usable rather than cramped compromises.
Why thirds and sixths finally make sense here
On a 3440px-wide display, a single third is roughly 1147 logical pixels — wider than an entire half of a 13″ MacBook screen. A sixth is around 573px, still enough for a chat app, a narrow reference panel, or a terminal without feeling squeezed. This is the opposite problem from a small laptop screen: instead of avoiding thirds because nothing fits, the challenge on an ultrawide is that halves alone waste the display’s actual advantage.
Rectangle app‘s relevant actions:
- ⌃⌥D / ⌃⌥F / ⌃⌥G — first, center, and last third
- ⌃⌥E / ⌃⌥T — first two-thirds, last two-thirds
- Sixths (top-left-sixth, top-center-sixth, and so on) are available but don’t have default shortcuts; assign them in preferences under the fuller action list if you plan to use a top/bottom split on top of thirds
A practical three-window layout
For a common setup — a main work app, a reference or documentation window, and a communications app — two-thirds plus a third outperforms three even thirds for most people, because it gives the primary app real working width instead of splitting everything equally regardless of how each app is actually used:
- ⌃⌥E (first two-thirds) — the app you’re actively working in
- ⌃⌥G (last third) — reference material, docs, or a terminal
If all three apps genuinely need similar space — three code editors, or three roughly equal reference documents — cycle through ⌃⌥D, pressing it again on the same window to move it to center-third, then last-third, and place one app in each position.
The 49″ super-ultrawide case: treat it like two monitors
A 5120×1440 super-ultrawide is wide enough that trying to manage it as a single canvas with thirds and sixths starts to feel arbitrary — the proportions don’t map cleanly to a 32:9 aspect ratio the way they do on a 21:9 screen. Many people managing a 49″ display do better treating the left and right halves as separate work areas, each internally split with its own halves or thirds:
- ⌃⌥← and ⌃⌥→ first, to divide the full width roughly into “left workspace” and “right workspace”
- Within each half, apply further halves or thirds to that half’s windows individually rather than trying to calculate sixths and eighths across the entire 5120px span
Rectangle mac‘s fraction actions are always calculated relative to the full display, not to a half you’ve already carved out, so this approach is manual layering rather than a single shortcut — but it maps much more intuitively to how a 32:9 screen is actually used than trying to keep six-way divisions straight in your head.
Where a single maximized window still wins
Not everything benefits from a multi-pane ultrawide layout. Video editing timelines, full-screen video calls, and games are usually better maximized (⌃⌥↩) across the entire width rather than sharing space with anything else — an ultrawide’s advantage there is the extra horizontal timeline or peripheral vision, not more windows crammed in. Don’t force a three-pane layout onto a task that’s better served by one app filling the whole screen.
Margins matter more at this width
If you’re running a pixel gap between tiled windows (set through Rectangle app‘s Terminal-based settings, documented in TerminalCommands.md), a gap that looks reasonable on a 27″ monitor can look sparse or, conversely, can add up to real wasted width across a three-or-four-window ultrawide layout, since the gap is applied at every boundary. Worth testing a smaller gap value specifically for ultrawide layouts rather than assuming the same setting that worked on a smaller display is still the right choice.
Quick reference
| Display | Suggested approach |
|---|---|
| 34″ ultrawide (3440×1440) | Thirds and two-thirds as primary tools; sixths for a narrow sidebar app |
| 49″ super-ultrawide (5120×1440) | Halves first to split into two workspaces, then thirds/halves within each half |
| Video, calls, games, any single-focus task | Maximize, regardless of screen width |