Tablets and smartphones range between 2 to 1000 nits. A mobile device becomes readable outdoors when it gets to 1,000 nits. Anything above 500 nits is good to use on a sunny day. Monitors and laptops range from 200 to 600+ nits.
Laptops: 200-600 Nits
It still needs a bright display, but it doesn't need to go as bright as it does on a smartphone. As such, a display of 200 to 600 nits will be good enough.
Technically, a device starts counting as “sunlight-readable” when it hits at least 1,000 nits, but very few mobile displays go that high. As a general rule, anything above 400 to 500 nits will do pretty well on a sunny day, but at 200 nits, you may have to find some shade to answer texts.
High brightness that would be in danger of damaging the eye would be in the neighborhood of 250,000 nits. That's why smartphones, computer screens, and televisions present no danger of eye damage according to clinical studies.
A monitor luminance of around 200-350 nits will work well indoors. Most LCD displays and monitors fall in this range. However, 400-700 nits would be required for use in daylight conditions. Most importantly, a Sunlight readable display requires at least 1,000 nits or more for viewing in direct, bright sunlight .
The more NITS the greater its brightness capabilities. That being said, screens intended for outdoor use need a greater NITS than screens for indoor use. When we're talking about indoor LED displays or fixed installation, we're looking for 1000-1500 NITS. Viewing conditions indoors are highly controllable.