DHT11 vs DHT22 — which temperature and humidity sensor to buy?

	DHT11	DHT22 (AM2302)
Temperature range	0–50 °C	−40–80 °C
Temperature accuracy	±2 °C	±0.5 °C
Humidity range	20–90 % RH	0–100 % RH
Humidity accuracy	±5 % RH	±2 % RH typical (up to ±5 %)
Resolution	1 °C and 1 % RH on most modules	0.1 °C and 0.1 % RH
Fastest reading	Once a second	Once every 2 seconds
Supply	3–5.5 V	3.3–6 V
Usual colour	Blue	White
Typical module price in India	₹60–120	₹180–320

They look alike, use the same three wires and the same Arduino library. The DHT22 costs two to three times as much — and for most real projects it’s worth it. Figures are from the manufacturers’ datasheets (Aosong for both); prices are indicative for 3-pin modules.

Why the DHT11 disappoints in India

Its range stops at 50 °C. A sensor in a sunny balcony, rooftop enclosure or tin shed in May can go past that.
±2 °C and whole-degree steps. Your room reads 31, then 33, with nothing in between. Fine for “is it hot?”, poor for a graph or a fan controller.
20–90 % humidity range. Monsoon air in Mumbai or Kerala sits above 90 % for days; the DHT11 can’t report it.

Where the DHT11 is fine

First experiments and school demos.
Indoor projects that only need a rough trend.
When you’re buying ten and the budget is tight.

Using either one

Same library (DHT sensor library by Adafruit). Change one word in the code: DHT dht(pin, DHT11); or DHT22. Picking the wrong type gives nonsense or failed reads.
3-pin modules have the pull-up resistor; a bare 4-pin sensor needs 10 kΩ from DATA to VCC.
Don’t read faster than the table allows — you’ll get the previous value or a failure.
Both work on 3.3 V boards (ESP32, Pico W) powered from 3V3.

Wiring guides: DHT22 with Arduino Uno, DHT22 with ESP32, and the DHT11 component page. Getting “Failed to read from DHT sensor”? See the fix.

Verdict

Buy the DHT22 unless the project is a one-off demo. If you need better accuracy than the DHT22, faster readings, or pressure as well, step up to an I2C sensor — DHT22 vs BME280 vs SHT31.