How many lumens do you need for a bike light?

Cycling Weekly's lights guide gives these rough minimums for the front light, with the rear light in brackets:

• Well-lit streets and paths: 50–300 lumens (rear 10–50)
• Partly lit streets: 200–400 (rear 25–100)
• Some unlit sections: 500–750 (rear 50–150)
• Totally unlit roads and paths: 750–1,000 (rear 150–300)
• Unlit country lanes and back roads: 1,000–1,500 (rear 150–300)
• Off-road at night: 1,500 or more (rear 150–300)

Faster riding needs more light, because you have less time to react to what the beam shows you.

Lumens measure how much light leaves the lamp, not where it lands. Beam shape decides how much of it is useful. A good front beam has a bright centre to pick out potholes and debris, and a wide spread so you can see the verge and other road users can see you.

Many German-style (StVZO) lights use a flat-topped beam that lights the road ahead without dazzling oncoming drivers. If you ride busy roads, that's worth looking for.

A bright flashing mode, front and rear, helps you stand out in grey weather and low winter sun. Flashing modes also give the longest battery life. For the front light, Cycling Weekly's author finds flashing distracting on the road and prefers a steady beam.

As Cycling Weekly summarises it, riding at night needs a front light, a rear light, a rear reflector and pedal reflectors. Flashing lights must meet a minimum output. Rules change, so check the current official guidance if you need certainty.

The Ravemen K1400 is Cycling Weekly's best front light overall, and its 1,400 lumens suit unlit lanes. For the rear, Cycling Weekly picks the Magicshine SEEMEE 300.