I find a lot of online tools to calculate the capacitance between two traces (or a trace and a plane) on opposite pcb layers. One such tool can be found here: http://chemandy.com/calculators/rectangular-capacitor-calculator.htm However, I would like to calculate the capacitance between adjacent traces on the pcb. Something like this: Has anyone an idea how to do this?

EDIT :
Imagine the following example:

• Two tracks run parallel for 10 mm.
• Each track is 0.2 mm wide.
• The distance between both tracks is also 0.2 mm.
• Copper thickness is about 20 µm.
• Board thickness is 1.6 mm.
• PCB material is standard FR4.
• One track is signal, the other Gnd.
• There are no other tracks in the area, nor any (Gnd-) planes.
• What is your end goal? Transmission line effects are usually the biggest concern over capacitance. – Voltage Spike Oct 18 '16 at 17:03
• The signal freq is rather low (250 kHz). The signal is in fact a pin from a capacitive sensor. So routing it parallel to a Gnd trace will cause some "capacitive offset". I'm trying to estimate that. – K.Mulier Oct 18 '16 at 17:14

• This is determined by copper thickness, gap, dielectric constant, d and length and thus there is incremental C and L with resulting impedance , Zo for a coplanar microstrip and thus C can be computed from this. For Zo=50R it is about 3.3pF /" or 1.3pF/cm

• So compute Zo from a coplanar stripline calculator (complex) then compute C from Zo as shown here. This assumes other conductors are >10x further away. If not then you have a mesh of calculations ;)

• If you can't find a coplanar stripline tool, try this formula.

$$\ C [pf/cm] = 0.12 * \dfrac{t}{w} + 0.09 * (1+d)*log_{10}(1 + \dfrac{2w}{g} + \dfrac{w}{g}^2)\$$

• w = width of track [mm]
• t = thickness of track [um]
• d = dielectric constant ~ 4.2 FR4
• g = gap [mm]

hopefully, I got the units correct...you do the math on a 50R pair.

The second term dominates. Using k=3.5 (kapton), w=10 mm, s = 0.5 mm, t = 2 microns, the capacitance is 1.1 pf/cm

• let's say I have two traces. One is a signal, the other is Gnd. They run parallel to each other for 1 cm. The copper thickness is 20 µm, the distance between the tracks is 0.2 mm. The tracks are also 0.2 mm wide.. – K.Mulier Oct 18 '16 at 15:56
• If the result is in pf/cm, how can there be l (length of paired tracks) in the equation. pf/cm suggests that the result is length independent but the equation itself required length, any thoughts on this? – Konstantin Dubovenko Jan 6 '19 at 5:13
• I checked my ref and the next post corrected it by comment – Tony Stewart Sunnyskyguy EE75 Jan 6 '19 at 9:47

I use ATLC for this. You can also draw your own setup (with the correct colours) and have it solve that. http://atlc.sourceforge.net/

• Thank you Matthew. This tool looks very promising indeed. Unfortunately, it seems a bit tough to get started with. I don't have the time to dig deeper into it. Do you know a good formula? – K.Mulier Oct 19 '16 at 12:43
• @K.Mulier I can't provide a formula, but I did use the tools to solve your problem - 63pF/m. If you are on Windows try this hdtvprimer.com/kq6qv/atlc2.html – Matthew Oct 19 '16 at 14:51
• Hi @Matthew, I've been trying to use ATLC2 to emulate your results and I'm getting values above 400pF. Is the value that ATLC converges on actually in pF/m? in the "results" panel, it only says pF... – Sean Dever Mar 10 at 22:51