Native Spells within Items ... How do I balance?

[Gix]

So I realize this is a 5E, how to GM well kind of thing and not a FG specific (at all) question.

In creating items and attempting to balance their power to the level of the character... and at the same time, make the items interesting, rather than just +1, which while useful, is rather boring, I am thinking of having the items be able to cast a particular spell or two.

I'm looking for more experienced 5E GM's to help me "right size" such abilities, and determine how, if at all, they should be limited.

Example: I have a holy weapon which I want to add some form of radiant damage to.

Branding Smite is a spell which is a bit more interesting than just damage.

So now I want to create a weapon which does something similar to that and deals radiant damage to boot.

Does anyone know of any resources for determining a balanced approach to magical items? Meaning say, Level 1-2, none; Level 3-4 don't exceed a +1, or a 1d4, or a level 1 spell twice per day... something like that.

[Zacchaeus]

You’ll find information about magic item level in the DMG and Xanathar expands on this considerably. Basically common and uncommon items are available at level 1-5, rare from 5-11 etc. So for what you want to do, take a look at existing magic items and see what sort of qualities that they have and then look at what sort of level that you might find that kind of property.

So something that adds the kind of damage that Branding Smite does might be equivalent to a Flame Tongue which would make it rare and available at around level 5 or higher.

Of course as DM you can ignore such restrictions but beware of giving out powerful magic too early lest you find your players are not being challenged.

[LordEntrails]

Also note that the DMG has secondary/minor type traits for magic items (like it tells you the depth under the ground, sheds dim light, etc) so you can give items those types of magical properties without making impacts to the power level.

[Gix]

Thank you gentlemen! Helpful.