How to measure capacity using oscilloscope ?

What we need:

- square wave generator (for example 100 Hz),
- resistor - 10kohm 1%, you must know precisely resistance
- oscilloscope

Measure schematic

voltage on the capacitor is equal to:

${\displaystyle V_{C}(s)={\frac {1/Cs}{R+1/Cs}}V_{in}(s)={\frac {1}{1+RCs}}V_{in}(s)}$
voltage on the resistor is equal to
${\displaystyle V_{R}(s)={\frac {R}{R+1/Cs}}V_{in}(s)={\frac {RCs}{1+RCs}}V_{in}(s)}$

Time charging or discharging the capacitor through the resistor is equal to:
${\displaystyle \,\!V_{C}(t)=V\left(1-e^{-t/RC}\right)}$
${\displaystyle \,\!V_{R}(t)=Ve^{-t/RC}}$
${\displaystyle \tau \ =\ RC}$

${\displaystyle \tau \ }$ 

T = RC

T - time when capacitor is charged to 63,2% of square wave amplitude [second]
R - resistance [ohm]
C - capacity  [farad]

When we know time (T) we can easy equal the capacity:

C = T / R

Before I start testing capacitor  I precisely measure resistance of resistor

Measure of resistor

 R = 9,9595 kohm

My testing board

 1 Measure voltage peak to peak of wave, in my case Vp-p = 5.16V
You must equal 63.2% of Vp-p,

Vm = Vp-p * 63.2%/100%

Vm = 3.26V

2 Now use cursors functionality in your oscilloscope and measure time between start rising curve and voltage measurement point (Vm = 3.26V in my case). 

T = 100 microsec (see delta X in the picture)

3 Equal the capacity:

C = T / R

C = 0.0000100 / 9959.5 = 0.000000001004 [F] = 10.04 [nF]

My measured capacitor have value 10 nF 1%