The BBFC rating page has a summary of what justifies their 12A rating, which may answer your question:
STAR WARS: THE FORCE AWAKENS is a sci-fi action adventure in which a
young woman becomes embroiled in a galactic conflict.
VIOLENCE There are frequent scenes of moderate violence, including use
of blasters and lightsabers, and dogfights between spaceships. Sight
of blood and injury detail is limited and brief.
THREAT Occasional scenes of moderate threat include characters being
interrogated using 'the Force', which it is implied causes them pain,
and characters being held at lightsaber-point.
There is infrequent use of very mild bad language ('hell', 'damn').
Unfortunately the only thing I can find for the corresponding American institutions is "Rated PG-13 for sci-fi action violence", which doesn't help much.
An unofficial site that often has more detailed ratings/summaries than the official ones is commonsensemedia.org, which says in the main summary:
Directed by J.J. Abrams, the sequel takes place approximately 30 years
after the events of The Return of the Jedi, and although there's tons
of sci-fi action -- space battles, crashes, explosions, lightsaber
duels, and more -- there's less violence overall than viewers saw in
Episode III: Revenge of the Sith. Villains do order the mass murder of
countless civilians, prisoners are coerced physically and with the
Force, and duels lead to injuries and death, but none of it is bloody
or gory. With little language ("dammit" and "hell" are as strong as it
gets) or sex, this is the kind of epic adventure that will undoubtedly
appeal to Star Wars fans of all ages. But while younger kids may be
familiar with the franchise and its many spin-offs (like the animated
Clone Wars), they might not be ready for some of The Force Awakens'
more violent or emotional scenes. (Spoiler alert: One death will hit
very hard.)
And in the tooltip of the "Violence" sub-rating:
Lots of sci-fci action violence on both the largest possible scale
(planets obliterated) and much smaller (one-on-one lightsaber duels
and firefights/shoot-outs), but hardly any blood/gore (with the
exception of bloody fingerprints on a white stormtrooper helmet).
There's a weapon that can destroy entire systems, and there are
explosive battle sequences in which people die and ships burst into
flames. Kylo Ren tortures people, both physically and with the Force.
Quick glimpses of dead soldiers and civilians lying around. Laser guns
of all shapes and sizes (handheld, ship mounted, etc.); bombs. Chases,
crashes, and frequent peril. Large, monstrous creatures rampage
through a ship; other creatures look scary/threatening, and the leader
of the First Order is creepy. A man orders an entire village of
civilians/witnesses slaughtered and cuts down an unarmed man. A young
man has debilitating anger issues. Spoiler alert: Supporting
characters are injured, one is presumed dead, and there's one very
upsetting death.
Having seen the film myself, I can attest these summaries are completely accurate, although the mention of "torture" in that last quote may sound worse than it actually is; it's more like "interrogation using the Force" as the BBFC summary says.
Whether this means 13, 10, 9, etc is the ideal cutoff is something only you can decide, but that ought to be enough detail for you to choose.
