Torricelli's Law (v = √(2gh))

Also known as tank drain velocity · efflux velocity

v = \sqrt{2 g h}

v =

h =

Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!

Constant used — built into this formula, no need to enter

g_{n} = 9.80665\ \text{m/s}^{2}

Standard acceleration of gravity · exact

Learning zone

Water leaving a hole in a tank exits exactly as fast as if it had free-fallen from the surface down to the hole — Bernoulli's equation with the pressure terms cancelled. A tap 5 m below the water line of a standpipe jets out at √(2 × 9.80665 × 5) ≈ 9.9 m/s. Notice what's absent: the fluid's density. Mercury and water pour equally fast from the same depth, just as a bowling ball and a marble fall equally fast.

Torricelli's Law (v = √(2gh))

v = \sqrt{2 g h}

Where

$v$ = Efflux speed
$h$ = Head above the opening

Missing one of these? Work it out first, then come back

Efflux speed — Speed, Distance & Time, Kinetic Energy
Head above the opening — Hydraulic Power (P = ρgQh), Pressure Head (h = P/ρg)