Last updated: March 2026
Delta allows 22 × 14 × 9 inches for carry-on bags. A 25L backpack sits well under that limit. Most 25L bags are compact enough to fit under a seat as a personal item — which is especially useful on some fares where carry-on access isn't included. Whether yours works under-seat depends on bag depth and structure, not just listed volume.
Check if this will actually fit your trip →Your result depends on what you pack, not just the bag size.
Based on real clothing volumes and packing behavior
| Max dimensions | 22 × 14 × 9 inches (55.9 × 35.6 × 22.9 cm) |
| Weight limit | No official weight limit on domestic routes |
| Personal item | Yes — one personal item allowed (under seat) |
| Carry-on access | Generally allowed; may vary by airline and boarding group |
| Fit at 25L | A 25L backpack usually works as a personal item — slim designs fit under most seats; bulkier builds may need overhead |
A 25L backpack falls well within Delta's published carry-on dimensions of 22 × 14 × 9 inches. At this size, the real question is not whether the bag is allowed — it's whether it works better as a personal item under the seat or as a compact carry-on in the overhead bin. Slim, soft-structured 25L bags tend to fit under most seats. Bulkier or more rigid designs may need overhead space.
For a full breakdown of size limits, boarding rules, and exceptions, see our airline carry-on rules guide →
Will a 25L backpack fit on United? →
Will a 25L backpack fit on American? →
Will a 25L backpack fit on Southwest? →
What to pack for a 3-day trip →
What to pack for a 5-day trip →
Not sure if it'll all fit? Try the packing calculator →
This tool reflects real-world packing conditions, not just theoretical bag sizes. Results are based on typical clothing volumes, packing efficiency, and common travel setups.
Published airline limits specify maximum external bag dimensions. A 25L backpack typically qualifies as a personal item, but this depends on the bag's external footprint and how it's packed — not just the listed volume. Slim, soft bags fit under most seats. Structured or rigid 25L designs may need overhead space.
This is a planning tool, not a guarantee. Airline staff make the final call — packed shape, bag rigidity, and gate-day enforcement all play a role.
This analysis is based on real packing volumes, airline dimension limits, and how soft-sided bags behave when packed.