The best G4 LED bulbs

For a run of warm under-cabinet or accent pucks, the BAOMING 10 pack - 350 published lumens at a published 2700K, which is the brightest warm figure in this group and works out at about $1.27 a bulb. If you want the most light the base can give you, the Gardencoin 4W publishes 480 lumens on a ceramic body, which is also the one to choose where the housing is tightly sealed.

Before any of that: check the voltage, not the base. G4 bulbs are sold in a 12V version and a 120V version that look identical and are not interchangeable. Find the transformer in your fitting first. If there is one, you want 12V, which is five of the six picks here. If there is not, you want the 120V version, and buying the other one is a wasted order rather than a dim light.

Everywhere else in the bulbs hub, the base is the whole fitment question: a GU24 twists in or it does not, an E12 screws in or it does not. G4 is the exception, because the base tells you almost nothing about the electrical system behind it.

The base was built for low-voltage halogen, so the great majority of G4 fittings run at 12 volts, fed by a transformer or driver hidden in the cabinet, the ceiling void or a landscape box outside. But G4 bulbs for 120V line voltage are also sold, for fittings wired straight to the mains - several listings put "120V" in the title precisely because buyers keep getting it wrong. Both are called G4. Both have 4 mm pins. Only one of them will work in your fitting.

So the first job is not shopping, it is looking. Open the cabinet, the junction box or the landscape housing and find the transformer. A box with a 12V output marked on it means 12V bulbs. No transformer anywhere in the circuit means line voltage, and the 120V bulb is the only pick here that suits you.

The naming rule is the same one that runs through this whole hub: in a G-series base, the number is the gap between the pins in millimeters. G4 is 4 mm. G9 is 9 mm and runs at line voltage in chandeliers and vanity bars. GU10 is 10 mm and twist-locks into track heads. GU24 is 24 mm and twist-locks into flush mounts. None of them interchange, and the number on the box is the only reliable way to tell.

The trap inside this page is GY6.35, at 6.35 mm. In a photograph it is a G4. In your hand it is a G4 with the pins slightly further apart and slightly thicker, and it is the base used where the original capsule was a larger 35W to 50W halogen - desk lamps, pendants, some accent fittings. If you ordered G4 and the pins will not line up with the holes, you own a GY6.35 fitting, and the TAIYALOO 4 pack is the version of this page's answer that fits it.

Physical size matters less here than it does on G9, where LED bodies are reliably bigger than the halogen capsules they replace and a close-fitting glass shade is the thing that decides. A G4 capsule usually sits inside a metal puck or a landscape housing with room around it. It is still worth a glance: the listings here describe T3 bodies, tubular at three eighths of an inch, so if your old capsule was noticeably slimmer than that, measure the space before ordering ten of them.

1. A published lumen figure. Four of the six state one, which is better than this base usually manages, and it is the only honest way to compare a 3W bulb against a 4W one.
2. A published color temperature. All six state one, and on a run of pucks a mismatched color is more obvious than a mismatched output.
3. Whether anything is said about CRI. One bulb publishes 85. The rest publish nothing, and this page says so rather than filling the gap.
4. What the voltage actually is. Five 12V and one 120V, chosen deliberately so that both kinds of fitting have an answer here.
5. Cost per bulb against pack size. These are bought ten at a time because fittings come in runs, so the pack price is the price that matters.

We did not test these; every figure is the listing's own and each one is linked below. Where a figure is not published - CRI on five of six, lumens on two - this page writes "not published" rather than estimating.

It is worth being realistic about the result, because G4 fittings are small and the numbers are small with them. Six of the brightest bulbs here is about 2,880 lumens on paper; six of the cheapest daylight ones is about 1,200. Those are ceiling-fitting figures spread across a whole counter run through small apertures, often behind a frosted cover that takes a further bite out of them.

That is enough for proper task light on a counter and nowhere near enough to light a kitchen. If the run of pucks is the only lighting in the room, the problem is not the bulbs - it is the plan, and how many lumens sets the target for the room while how many bars does the same for the counter specifically.

The other honest comparison is against replacing the fittings outright. A ten pack of bulbs is a few dollars a fitting; a set of modern LED pucks is a great deal more, and the picks for that are in the best LED puck lights. Re-lamping is the right first move when the housings are sound and the wiring works. Replacing is the right move when the fittings are failing, the color is wrong at the fixture level, or you want something dimmable and the transformer will not cooperate.

BAOMING G4, 3.5W, 2700K, 10 pack - the pick. 350 published lumens at a published 2700K, with a no-flicker claim, at the lowest cost per lumen on this page.
Who it is for: a run of warm under-cabinet or accent pucks on a 12V transformer. Who should skip it: anyone whose fitting is on a dimmer - there is no dimming claim here.
Cons: no CRI published; no dimming claim; the 20W-to-30W equivalence range is as loose as the rest of the base; 12V only.

Gardencoin G4, 4W, 480 lm, 10 pack - the most output, and the one for a sealed housing. 480 published lumens at 2700K with a 360-degree beam and a ceramic base.
Who it is for: tight, closed puck housings, and any fitting where the old halogen was genuinely bright. Who should skip it: anyone counting pennies - it is twice the price per bulb of the cheapest pick.
Cons: no CRI published; no dimming claim; 4W is the most heat of the 12V picks here, which is exactly why the ceramic base matters.

Letaclanic G4, dimmable, 3000K, 10 pack - the only 12V dimming claim. 3W at a published 3000K across a 12V to 24V range, in a silicone body.
Who it is for: a low-voltage fitting that already has a dimmer on the wall. Who should skip it: anyone who needs to know the output - this publishes no lumen figure at all.
Cons: no lumens and no CRI published; a dimming claim is not a transformer compatibility promise; 30W equivalence with nothing published to check it against.

DiCUNO G4, 2W, 6000K, CRI 85, 10 pack - the one with a color-rendering number. 200 lumens at 6000K with CRI 85 published - the only CRI figure found anywhere on this base - and the cheapest bulb here.
Who it is for: a work surface, a garage bench or a utility cupboard where seeing detail beats atmosphere. Who should skip it: a kitchen you eat in, or any run that already has 2700K bulbs in it.
Cons: 6000K is cold daylight and unforgiving indoors; lowest published output of the 12V picks; non-dimmable, stated.

DiCUNO G4, 120V, dimmable, 2700K, 10 pack - for a fitting with no transformer. 1.5W at 2700K and 160 published lumens, built for line voltage, with a dimming claim.
Who it is for: G4 sockets wired straight to the mains - some ceiling and under-cabinet puck fittings genuinely are. Who should skip it: everyone with a transformer, which is most people - in a 12V fitting this will never light.
Cons: lowest published output on the page; no CRI; it is a 15W halogen replacement, which is a smaller capsule than many G4 fittings carried.

TAIYALOO GY6.35, 5W, 3000K, 4 pack - the base that is not quite G4. 6.35 mm pin spacing at 12V, 3000K, in the wattage the bigger capsules used.
Who it is for: desk lamps, pendants and accent fittings where a G4 bulb arrives and will not seat. Who should skip it: anyone whose fitting is genuinely G4 - the pins are too far apart and it will not go in.
Cons: no lumen or CRI figure published, so the 50W equivalence claim cannot be checked; non-dimmable; about $4.50 a bulb, three times the G4 picks.