A soil moisture meter is a handheld tool that measures how much water is in the soil to take the guesswork out of watering plants. You insert the probe into the ground and it gives you a reading—usually on a dial, LED scale, or digital screen—showing if the soil is dry, moist, or wet. Most basic models are analog and don’t need batteries, while advanced ones also measure light and pH. It helps prevent overwatering and underwatering, which is the fastest way to keep houseplants and garden beds healthier.