Arc length calculator

Let’s say you wanted to figure out angles based on a desired arc length and radius, the math is nasty.

Alternately, you can go here:

Yeet! Angles everywhere.

Alternately, for a given angle and radius you can determine the arc length.

It’s highly specialized, but it sure helped me out for this really specific thing I am doing. I haven’t explored, but they have a lot of other calculators. Let’s see… Oh wow, there are a lot. You’ll just have to poke around.


Nice find!

Maybe its from growing up as a land surveyor, but arc length/angle isn’t hard. It is just the fraction of the total circle. This is actually a simple equation to derive. If you know arc length and radius, you can find the circumference and then it is simple division to find the included angle. If you know radius and angle, you find the circumference and then it is simple division to find the arc length.

Chord is a little more challenging, but even that isn’t hard once you know the included angle. The chord is twice the length of the opposite side of a right triangle of half the included angle.

The tricky ones are spiral curves. Normal curves are easy.


Cool, bookmarked.

Yeah, I don’t have a problem with arc length calculations either, but if you home on the Omni, there are a slew of handy calculators there for just about everything under the sun. Good find! :sunglasses::+1:

I thought Ark lengths were done in cubits. :rainbow:

That’s a nice find. I am forever looking for special equations. Been doing some truss calculators lately.


How many of each animal did Moses take on the Arc? :grin:

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This one is fun…how many helium balloons would you need to levitate? :smile:



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i’m not sure the accuracy of the extension but have you tried using the “measure path” in inkscape.
Extensions > visualize path > measure path

Yup, I like that path length feature. In this case I needed the angles that several arcs of specific lengths would require. It can be done by some fairly straightforward algebra, or I could find a calculator that does it the quick way, so here we are.

My backup was google sheets, but it was only 7 arcs, so that seemed like overkill.

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I assumed you would know about that feature but figured i would throw it out there anyway as i just discovered it yesterday :stuck_out_tongue_winking_eye:

OK, OK, that’s a good one. I’ll offer one you may already know for you:

Select a vector shape, duplicate it, then hit Shift G to automatically convert it to guides. You’ll have a copy of your original shape with tons of guides snapped to it, thusly:


cool i’ve only ever done that on accident never really knew a use for it.

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If you ever try to make your own geometric tilings or patterns, you live and die by guides.

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Still learning, i have a bad habit only looking for solutions to problems i know i have. I really need to actually learn how to use inkscape properly and not just muddle my way through lol. im sure a graphics design course would help as well.

Well to me the way I learn is that I have to have a problem first and then I figure out how to solve for it. I do lots of geometric projects and lots of pattern stuff. Precise alignment on stuff like that is key, so I’ve gotten really proficient at using guides.

This arc calculation thread is an example of this, I needed to be sure some stacked layers would be offset precisely, and now here we are.


That is something ive been wanting to get into but when i tried (not very hard) was having symmetry issues and stuff like that, so i put it on the back burner till i had more time for it. using guides like this will help me greatly. there are at least dozen tips and tricks i’ve picked up from you in the past that make my life easier, Thx for that

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That’s good to know. Could have used that in the spiderweb build. I do need to read through the shortcuts in Inkscape more often to remind myself of what is out there.