The headline number on a torch is lumens, but lumens only tells you how much light comes out, not where it goes. For lighting a path, a campsite or the inside of a cupboard, lumens is a fair guide. For seeing something a long way off, the number that matters is candela, and its companion, beam distance. And whatever the box says, a bright torch usually holds its top setting for only a minute or two.
The standard behind the numbers
Most reputable torch makers measure their lights to the same voluntary standard, ANSI/PLATO FL 1, first published in 2009 and revised since. When you see these little icons on a box, the torch was tested to it:
A box with big numbers and none of those icons may be honest, or may not. A “20,000-lumen” torch the size of a pen, from a seller you’ve never heard of, is not.
Lumens: how much light
Lumens is the total amount of visible light leaving the torch, measured in a sphere that catches all of it. Under FL 1 it’s measured 30 seconds after switch-on with fresh batteries. That detail matters, as you’ll see under runtime.
As a rough guide: a phone torch is somewhere around 50 lumens; 100 to 300 lumens is plenty for walking a track or finding something in a dark room; 1,000 lumens lights up a whole backyard. More lumens also means more heat and flatter batteries.
Candela: how concentrated
Candela is the intensity of the brightest part of the beam, the “hotspot”. Two torches with the same LED and the same lumens can have very different candela figures, depending on the optic in front of the LED:
- A deep, smooth reflector squeezes the light into a tight spot that reaches a long way: a thrower. High candela.
- A shallow or textured reflector, or a diffuser, spreads it into a wide, even pool: a flooder. Low candela.
That’s why a 300-lumen torch built to throw can show you a kangaroo 150 metres down a fire trail, while a 1,000-lumen flooder lights everything near you and fades out well before that. Neither is better: a headlamp for camp chores should flood; a torch for checking what made that noise should throw.
Beam distance: worked out from candela
Beam distance is how far away the centre of the beam has faded to 0.25 lux, which is roughly the light of a full moon on a clear night. It isn’t measured with a tape: it’s calculated from the candela, because light fades with the square of the distance.
Beam distance in metres = 2 × √candela. So 1,000 candela gives about 63 m, 10,000 candela gives 200 m, and 40,000 candela gives 400 m. Notice what that means: to double the reach, a torch needs four times the candela.
Bear in mind “full moon” isn’t much light. At the quoted beam distance you’ll see that something is there; to see clearly what it is, you need to be a good deal closer. Try it below.
Beam distance calculator
Runtime, and why bright torches dim
FL 1 runtime is the time from that 30-second reading until the output has fallen to 10% of it. Two things follow from that definition.
First, most bright torches step down. An LED driven hard gets hot fast, and so does the battery, so the torch drops itself to a lower level after a minute or two, or when it senses heat. That’s good engineering, not a fault. But the 1,000 lumens on the box may only last 90 seconds before the torch settles at 300.
Second, a runtime can be honest and still tell you little. Say a torch starts at 1,000 lumens, steps down to 300 after two minutes and holds that for three hours, then fades. Its runtime on the 1,000-lumen setting is quoted as about three hours, because it hadn’t yet dropped below 100 lumens. The box doesn’t say that you had 1,000 for two minutes of it.
Good makers publish a runtime graph, output against time, in the manual or on their website. It’s the most useful picture of a torch there is: look for a flat line at a level that suits you, rather than a tall spike at the start.
Drops and water
Impact resistance is the height in metres from which the torch was dropped onto concrete and still worked, with no cracks. One metre is common; two metres is better for a torch that lives in a ute.
Water resistance uses the IP code’s water digit:
| Rating | What it survived | In practice |
|---|---|---|
| IPX4 | Splashing from any direction | Rain is fine; don’t drop it in a creek |
| IPX7 | Submerged to 1 m for 30 minutes | A dunking, a wet canoe, a torrential downpour |
| IPX8 | Submerged deeper than 1 m, to a depth the maker states | Check the depth; it’s still not a dive torch unless it says so |
Colour: warm, neutral or cool
LEDs come in different tints, given in kelvin. Below about 3,500 K looks warm and yellowish, around 4,000 to 5,000 K neutral, and 6,000 K and above cool and bluish. Cool LEDs often squeeze out a few more lumens, which is why they’re common. Some torches also quote CRI, the colour rendering index: 90 or more means reds, browns and greens look the way they do in daylight. That helps when you’re reading a map, tracing wires or telling a brown snake from a stick.
Batteries
The battery decides how big the torch is, how long it runs and how easy it is to feed.
- AA and AAA. Available anywhere. Rechargeable NiMH cells are the best everyday choice; lithium AAs are light, last for years in a drawer and work in the cold. Alkalines are fine for an emergency torch, but check them yearly, because a leaking alkaline can wreck a torch.
- CR123A. A 3-volt lithium cell, common in compact, bright torches. It stores for years, but it isn’t rechargeable. See CR123A and its equivalents.
- 18650 and 21700. Rechargeable lithium-ion cells, 18 mm and 21 mm across, about 3.6 to 3.7 V nominal and 4.2 V when full. They power most bright torches now. See the 18650 and its family.
Lithium-ion cells need a little care:
- Ignore huge capacity claims. Good 18650s reach about 3,500 mAh and good 21700s about 5,000 mAh. A “9,900 mAh” 18650 is a fake, usually a much smaller cell in a big wrapper.
- Match what the torch asks for: button top or flat top, protected or unprotected. Protected cells have a small circuit that cuts off before the cell is over-discharged or shorted, and are a few millimetres longer.
- Carry spares in a case. A loose cell in a pocket with keys or coins can short out, get very hot and burn you.
- Charge them on a proper lithium-ion charger, and stop using any cell with a torn wrapper or a dent.
To check how much is left in a cell, our guide to measuring battery voltage has a lithium-ion chart.
Choosing one
- Everyday carry: small, a pocket clip, 300 to 1,000 lumens, a single AA or 18650, and a low “moonlight” mode that won’t wake the house.
- Bushwalking and camping: a headlamp first, so your hands are free, with a red mode to keep your night vision. Then a small torch as a spare.
- Searching or spotting: look at candela, not lumens. Tens of thousands of candela for hundreds of metres.
- Car, caravan or emergency kit: a torch that takes AA cells, with lithium AAs that keep for years.
Whatever you buy, read the runtime graph, and buy from a seller with a real return policy. And take a compass as well as a torch into the bush: batteries go flat, a needle doesn’t.
Common questions
Are more lumens always better in a torch?
Why does my torch get dimmer after a minute or two?
What does beam distance mean on a torch?
What is the difference between IPX7 and IPX8 on a torch?
Sources
All checked 11/11/2026. We don’t sell torches, and none of these links earns us anything.
- Streamlight, ANSI/PLATO FL 1: Flashlight Basic Performance Standard (definitions of light output, runtime, beam distance, impact and water tests). streamlight.com
- Pelican, Flashlight ANSI Standards (0.25 lux and the full-moon comparison). pelican.com