Short answer: pick the ST58 for tight fixtures and subtle style. Pick the ST64 when the bulb itself should be the star.
The difference is size, and only size. The ST64 is the larger bulb, and the ST58 is the smaller one, according to Edison Mills.
Who this guide is for
You are staring at a pendant lamp and two nearly identical bulbs. Both look like they came from a Victorian workshop. Only the number differs.
This guide covers:
- What the codes actually mean
- How the two shapes differ
- Which one suits which room
- What to check before you click "buy"
What do ST58 and ST64 actually mean?
The letters describe the shape. The number describes the diameter, as LEDMUNDO's shape-code guide explains.
- ST = straight tapered, the classic teardrop Edison outline
- 58 / 64 = diameter in millimetres (metric labelling)
- ST18 / ST21 = the same bulbs labelled in the US inch system
So a fixture that asks for ST58 wants the same bulb as ST18, as Nostalgic Bulbs notes. Shops just label them differently.
ST58 vs ST64: side-by-side comparison
| Feature | ST58 | ST64 |
|---|---|---|
| Size | Smaller | Larger |
| Inch-system code | ST18 (2.25" diameter) | ST21 |
| Typical height* | About 5.25" | About 5.5" |
| Typical width* | About 7.5" around | About 8" around |
| Top of bulb* | Teardrop tip | Rounded bulge |
| Filament style* | Squirrel cage | Squirrel cage |
*Figures come from one seller's answer on an Amazon product Q&A. Another customer answer notes that sizes vary between manufacturers. Always check the spec sheet.
How big is the real-world gap?
Small. One seller puts the ST64's diameter at about a quarter inch more than the ST58's.
That sounds tiny. It matters inside a snug glass shade or a wire cage.
Which bulb suits which space?
Choose the ST58 if you have:
- Small glass shades or cages
- Bedside lamps and compact sconces
- A taste for subtle vintage style
- Several bulbs in a tight cluster
Choose the ST64 if you have:
- Bare-bulb pendants hanging from a cord
- High ceilings that swallow small bulbs
- Cafés, kitchens or bars needing a bold look
- Open fixtures with plenty of clearance
Rule of thumb: if the bulb shows, go bigger. If a shade hides it, go smaller.
Does size change brightness?
No. Wattage measures power use, and lumens measure brightness, as this lighting retailer explains. Shape does not decide either number.
Check the box for these values instead:
- Lumens: the actual brightness
- Kelvin (K): the colour of the light
- Dimmable: yes or no, printed on the pack
Which colour temperature works best?
Lower Kelvin gives a warmer, yellower light. Energy Trust of Oregon says people usually prefer about 2700K in living rooms, bedrooms and dining rooms, in its bulb colour guide.
| Kelvin | Look | Suggested use (Energy Trust) |
|---|---|---|
| Around 2700K | Warm, yellow | Living rooms, bedrooms, dining rooms |
| Around 3500K | Cool white | Kitchens and work spaces |
| Around 5000K | Bright daylight | Reading lights and desk lamps |
Vintage bulbs usually look best at the warm end. Nobody wants a hospital-white Edison bulb. It ruins the joke.
Five-point checklist before you buy
- Measure your fixture. Check the opening and the clearance around the bulb.
- Check the base. Risun notes that E26 is the common screw size in North America. The UK retail listings we reviewed use E27.
- Read the lumens. Ignore the shape when judging brightness.
- Confirm dimming. Buy a dimmable bulb only if your dimmer supports it.
- Compare specs, not just codes. Manufacturers vary in exact size.
Common mistakes to avoid
- Assuming ST58 and ST18 are different bulbs (they are not)
- Buying an ST64 for a shade with no spare room
- Judging brightness by bulb size
- Choosing cool white and wondering why the vintage look vanished
Frequently asked questions
Is ST58 the same as ST18?
Yes. Both codes describe the same size, one in millimetres and one in the inch system, per Nostalgic Bulbs.
Can I swap an ST58 for an ST64?
Often, yes, if your fixture has room. The ST64 is slightly larger, so measure first.
Is the ST64 brighter?
Not by shape. Compare lumens on the pack instead.
Which one looks more "vintage"?
Both do. The ST64 simply makes a louder statement.
Keep exploring
Lighting is one piece of a cosy home. These guides pair well with this one:
- Cozy Cocooning: Designing a Home You Never Want to Leave
- How Modern Window Glass Can Improve Comfort and Reduce Energy Costs
Final verdict
- ST58: compact, subtle, fits more fixtures
- ST64: larger, bolder, best when the bulb is on show
- Either way: check lumens, Kelvin and dimming
Short answer: pick the ST58 for tight fixtures and subtle style. Pick the ST64 when the bulb itself should be the star.
The difference is size, and only size. The ST64 is the larger bulb, and the ST58 is the smaller one, according to Edison Mills.
Who this guide is for
You are staring at a pendant lamp and two nearly identical bulbs. Both look like they came from a Victorian workshop. Only the number differs.
This guide covers:
- What the codes actually mean
- How the two shapes differ
- Which one suits which room
- What to check before you click "buy"
What do ST58 and ST64 actually mean?
The letters describe the shape. The number describes the diameter, as LEDMUNDO's shape-code guide explains.
- ST = straight tapered, the classic teardrop Edison outline
- 58 / 64 = diameter in millimetres (metric labelling)
- ST18 / ST21 = the same bulbs labelled in the US inch system
So a fixture that asks for ST58 wants the same bulb as ST18, as Nostalgic Bulbs notes. Shops just label them differently.
ST58 vs ST64: side-by-side comparison
| Feature | ST58 | ST64 |
|---|---|---|
| Size | Smaller | Larger |
| Inch-system code | ST18 (2.25" diameter) | ST21 |
| Typical height* | About 5.25" | About 5.5" |
| Typical width* | About 7.5" around | About 8" around |
| Top of bulb* | Teardrop tip | Rounded bulge |
| Filament style* | Squirrel cage | Squirrel cage |
*Figures come from one seller's answer on an Amazon product Q&A. Another customer answer notes that sizes vary between manufacturers. Always check the spec sheet.
How big is the real-world gap?
Small. One seller puts the ST64's diameter at about a quarter inch more than the ST58's.
That sounds tiny. It matters inside a snug glass shade or a wire cage.
Which bulb suits which space?
Choose the ST58 if you have:
- Small glass shades or cages
- Bedside lamps and compact sconces
- A taste for subtle vintage style
- Several bulbs in a tight cluster
Choose the ST64 if you have:
- Bare-bulb pendants hanging from a cord
- High ceilings that swallow small bulbs
- Cafés, kitchens or bars needing a bold look
- Open fixtures with plenty of clearance
Rule of thumb: if the bulb shows, go bigger. If a shade hides it, go smaller.
Does size change brightness?
No. Wattage measures power use, and lumens measure brightness, as this lighting retailer explains. Shape does not decide either number.
Check the box for these values instead:
- Lumens: the actual brightness
- Kelvin (K): the colour of the light
- Dimmable: yes or no, printed on the pack
Which colour temperature works best?
Lower Kelvin gives a warmer, yellower light. Energy Trust of Oregon says people usually prefer about 2700K in living rooms, bedrooms and dining rooms, in its bulb colour guide.
| Kelvin | Look | Suggested use (Energy Trust) |
|---|---|---|
| Around 2700K | Warm, yellow | Living rooms, bedrooms, dining rooms |
| Around 3500K | Cool white | Kitchens and work spaces |
| Around 5000K | Bright daylight | Reading lights and desk lamps |
Vintage bulbs usually look best at the warm end. Nobody wants a hospital-white Edison bulb. It ruins the joke.
Five-point checklist before you buy
- Measure your fixture. Check the opening and the clearance around the bulb.
- Check the base. Risun notes that E26 is the common screw size in North America. The UK retail listings we reviewed use E27.
- Read the lumens. Ignore the shape when judging brightness.
- Confirm dimming. Buy a dimmable bulb only if your dimmer supports it.
- Compare specs, not just codes. Manufacturers vary in exact size.
Common mistakes to avoid
- Assuming ST58 and ST18 are different bulbs (they are not)
- Buying an ST64 for a shade with no spare room
- Judging brightness by bulb size
- Choosing cool white and wondering why the vintage look vanished
Frequently asked questions
Is ST58 the same as ST18?
Yes. Both codes describe the same size, one in millimetres and one in the inch system, per Nostalgic Bulbs.
Can I swap an ST58 for an ST64?
Often, yes, if your fixture has room. The ST64 is slightly larger, so measure first.
Is the ST64 brighter?
Not by shape. Compare lumens on the pack instead.
Which one looks more "vintage"?
Both do. The ST64 simply makes a louder statement.
Keep exploring
Lighting is one piece of a cosy home. These guides pair well with this one:
- Cozy Cocooning: Designing a Home You Never Want to Leave
- How Modern Window Glass Can Improve Comfort and Reduce Energy Costs
Final verdict
- ST58: compact, subtle, fits more fixtures
- ST64: larger, bolder, best when the bulb is on show
- Either way: check lumens, Kelvin and dimming
