How do you measure the back length of a violin

July 6, 2023, 4:07 PM · The conventional way is to use fabric or plastic measuring tape, and follow the instructions here:

https://www.wikihow.com/Measure-the-Body-Size-of-a-Violin,-Fiddle,-Viola,-Cello-or-Upright-Bass

You can't use a straight ruler. An alternative is to use a large caliper, but this gives a different measurement value than the more widely used tape measure.

July 6, 2023, 5:09 PM · You can use a flexible metal or plastic straight ruler, that's what I use

July 6, 2023, 5:30 PM · So the length includes the curvature and arch of the back?

If one includes the arch/curvature, the measurements would be longer length, no?

Guarneri models are known for the higher arching, but are typically measured as smaller than Stradivari models.

I guess I am confused. Or maybe my question is not understood.

Bottom line — is the violin length a straight line from point A to point B, excluding the arching?

Edited: July 6, 2023, 9:05 PM · "Bottom line — is the violin length a straight line from point A to point B, excluding the arching?"

Measurements made with measuring tape include the arching. Measurements made with calipers do not include the arching.

Most reported measurements were made with measuring tape unless otherwise specified that they were made with calipers.

Edited: July 7, 2023, 12:41 AM · According to my rough calculation if the arching is 1 cm deep the difference between the straight top-tail measurement and the curved one that includes the arching would be between 0.5 and 1 mm. In the overall scheme of things this seems pretty insignificant.

July 7, 2023, 5:05 AM · Some measurements are taken with calipers. More often, they are taken with a tape or flexible ruler. It's nice when they specify which was used...

Edited: July 10, 2023, 10:58 AM · @George Huhn - my brain "melted" when you stated measurements typically include arching.

@David Burgess - my brain "doubly melted" when you confirmed George's statement.

Violin-making is exacting and precise. The standard definition is not clear to lay person.

@Steve Jones - thank you for your math skills in calculations. I can neither confirm nor refute your numbers. My real numbers this morning is that the length of my violin is 36cm with flexible sewing measuring tape, and 35.6cm with a long straight sewing rule. Measuring with straight rule is hardest with hand, eye coordination, and the violin hanging straight down. IMHO- I believe its more than 0.5-1mm difference that you have kindly calculated.

This brings up other questions:

How to interpret numbers listed online from a reputable violin store?
How to interpret numbers from Tarisio auctions?

How to interpret numbers from a violin maker? For example, I am looking at a booklet of a specific violin, front length is 356mm, and back length 357mm, and it has separate measurements for lower bout, upper bout etc. Would it be a good assumption that if it is from a violin maker, measurements would be from calipers?

Thank you in advance to all for answering. I have a curious mind. Sorry for any stoopid questions:(

July 7, 2023, 8:20 AM · I'm afraid this is a "grey area" - one of many in the violin business.

Edited: July 11, 2023, 9:29 AM · It seems obvious to me that what makes sense for "player sizing" is the straight-line distance from "point A" to "point B" (whatever those points are on the instrument and ignoring any "Einsteinian general relativistic corrections" for "space curvature" (:-)).

P.S. This would also apply to the problems of wood dimensions for makers and and viola case dimensions selection for buyers.

Edited: July 7, 2023, 10:47 AM · Unless otherwise noted, you can assume it was measured conventionally using a tape measure. Using a straight flat ruler to try to estimate the length by eyeballing it would be very inaccurate.

Similarly, widths of the bouts are also usually measured with tape measures over the arching.

In most cases, caliper measurements are not used because most people don't have large calipers. Furthermore, because caliper measurements are shorter than tape measurements, the caliper measurements should be reported "by caliper."

July 7, 2023, 12:17 PM · I always mention the size of my violas as "caliper", and not "LOB" (length over the back). Technical books will always be in caliper too.

July 7, 2023, 8:31 PM · It makes plenty of sense to me to measure over the arch with a measuring tape. Violins don’t have flat plates, and there’s no reason to treat them as if they do. Caliper measurements are useful as well, but most of the time it’s a lot less convenient to use them, and a caliper is not necessarily any more accurate than a caliper. Some posters or other technical sources specify the measurement tools or list both measurements, but when a back length is given, you should assume it’s taken with a tape unless described otherwise.

July 7, 2023, 10:19 PM · It seems to me that the primary reason for using the flexible tape is to avoid the parallax that one would suffer in aligning the marks of a rigid ruler placed along the arch with the edges of the back.

Here's how the math works. Let's say you have a 16-inch viola and the height of the arch is 0.5 inch. Then the arch rises by half an inch over nine inches from top to middle, and back again from middle to bottom. So, to a first approximation the distance from the edge to the middle is the hypotenuse of a right triangle having edges 9 inches and 0.5 inches. The Pythagorean theorem gives this length as 9.014 inches. The additional 0.014 inches corresponds to 0.35 mm. Doubling this gives 0.7 mm. The curvature of the back is not linear, of course. It's more sigmoidal, which will give a somewhat higher error. If my approach is correct, then the maximum error is one inch, if the curvature of the back was a step function (i.e., not gradual at all).

July 7, 2023, 11:08 PM · Cloth fabric tapes are notoriously inaccurate, that would explain the crazy numbers people are getting with them

Edited: July 8, 2023, 1:28 AM · @Paul - that was how I calculated it, until your last sentence that defeats me...

I gather there is indeed some prejudice in the violin world against instruments exceeding 360 mm but why this should be so is unclear. From the point of view of fingering surely it's the vibrating string length that's critical? And viola players don't seem to have many problems adapting to (much) larger or smaller instruments. That said, I have difficulty adapting to a 362mm violin with an unusually low ratio between the neck stop and the body stop; this means that with my thumb on the crook of the neck I have to stretch the hand more to reach the higher positions.

Edited: July 11, 2023, 7:07 AM · @George Huhn - thank you for clear concise clarification. I really appreciate that. Thanks for including that curvature measurements are for bouts as well.

This way of measuring must be obvious to those in the violin world. I only get to "read" about it, and look at pictures. Most drawings for length is a straight line from point A to point B. If the drawing was a curved line between point A to point B hugging the arch, it would have made more sense to lay person like me.

@Luis Claudio Manfio - Thank you for input. I looked at the booklet of the violin measurements from violin maker. There is no mention of "caliper." There is a straight line from point A to point B, BUT the line is broken like this ——- - - 356 - - - ——. I gather this means measured with flexible tape?

@Lyndon Taylor - I did double check sewing rule, fabric measuring tape with other "yardsticks" and they are good. You are right that measuring tapes can be inaccurate.

Ok- this has been educational. I find out that I am playing a violin that is larger than I thought I could handle [being petite etc.] Also this violin is supercomfortable for me, probably because of luthier set-up, maybe?

I also now wonder how one could transition from 360mm to say ?355mm and not lose muscle memory of left hand. Spacing would be different. Or can a quick adjustment be made. I believe I read somewhere on this site, that recommendation is to stick to one and not play both.

UPDATE: I made a mistake in measuring. My violin is ~355mm. So please DO NOT assume 360mm is OK for petite frame.

Edited: July 8, 2023, 12:53 PM · Lisa wrote, "I also now wonder how one could transition from 360mm to say ?355mm and not lose muscle memory of left hand. Spacing would be different."

Not necessarily. If the string length (distance between the bridge and nut) and the action are the same, the fingering will remain the same.

Note that string length often varies a few mm between violins with the same LOBs. It depends on the individual violin and the set-up.

Edited: July 9, 2023, 6:36 PM · Steve Jones,

Violin shops tend to eschew violins over 360 mm, not because of vibrating string length, which can be adjusted, but because of the additional volume of the body, which tends to make a violin more viola-like. This is actually a thing that fiddlers like, so the longer instruments tend to either be rejected altogether by shops or set aside in case a fiddler comes in.

Cloth measuring tapes are not generally the type used for measuring instruments, so their inaccuracies are not relevant. Good quality metal tapes are consistent enough that back measurements are fairly easy to take. Problems arise when people don’t know where to place the tape or when they’re measuring things like bout widths, which are a little trickier to measure.

Edited: July 9, 2023, 11:33 PM · Sorry Rich but the volume explanation doesn't hold water for me. Among the violins that adorn my wall I have two that measure 362 mm; one of them indeed sounds quite viola-ish while the other doesn't. The former actually has the lowest ribs of all my violins (its arching compensates to some degree) while a third one with very high ribs that I wondered might be a tiny viola doesn't sound anything like one! The two UK dealers and one auctioneer that I've discussed this with are similarly unsure of the reason why half a centimeter in length is deemed to have such significance but are reluctant to swim against the commercial tide so tend not to stock or promote larger instruments.

Edited: July 10, 2023, 11:32 AM · @Lyndon Taylor & @Rich Maxham – I hear an echo here which is “my measurements are inaccurate.” For kicks and giggles, I went ahead and took a metal tape and measured. The metal tape hooked to wood tail end, touches the highest arch, and to the top imaginary line above the purfling. It is 354.5 to 355mm. The fabric measuring tape is 360mm. My human eyes “see” that metal and fabric tape correspond well side by side. 5mm is huge, so I double-checked - I was looking at the wrong line on fabric tape. DOH! It is ~355mm by fabric tape.

Mea culpa. I feel stoopid. If I made any clothes, it would be lop-sided.

@George Huhn – thank you. The violin is complex. I learnt something new from your comments.

July 10, 2023, 2:31 PM · Lyndon, I agree cloth tapes are inaccurate. Would it be possible to take a sheet of paper, place or on the back of the violin, mark the 2 points on the paper, remove it from the violin and then measure them with an accurate ruler? Would this account for the arc?

July 10, 2023, 2:47 PM · that would add the arc, might as well just use a flexible ruler or tape measure

July 10, 2023, 4:28 PM · I think that the most indicative measurement from the violinist's point of view is the linear one taken with the caliper, as this determines the distance from the hand to the violinist's neck (which is linear, not curved) and so the needed extension of the left arm. Of course it is more handy to measure with tape, but if the arching is very high the measurement is decidedly stretched, and therefore distorted. As a luthier, I consider the measurement with the caliper to be the only reliable one, the one with the tape only serves to have a very inaccurate general idea, which generates a lot of confusion for a luthier that is always dealing with linear measurements.
In any case, it is essential to specify how the measurement was taken, because the caliper and the tape always give two different numbers.

Edited: July 10, 2023, 7:48 PM · The problem with cloth tapes is that they're stretchy. A flexible metal tape would be better but then you risk scratching the instrument trying to follow its contour.

Steve, about the calculation, imagine the curvature of a 16-inch viola back being as follows. Perfectly flat for 7 inches, then perpendicular to that for 0.5 inch, then flat for another inch. Mirror that on the other side. Ignoring the "curvature" you'll measure 16. If you follow the "curvature" closely using an infinitely flexible tape, you'll measure 17 (7 + 0.5 + 1)x2. The linear shape that we used for our calculations is the most gradual possible curvature, giving an error of less than a millimeter overall. The "perpendicular step up and step down" is the most extreme possible monotonic contour, giving an error of an entire inch!! The true curvature is (obviously) between these two extremes and seems likely to be much closer to the linear model, but what these calculations show is that the exact curvature does influence the amount of error.

Thinking about the caliper reminds of the old days when you would go to a shoe store and have your foot measured using this particular device that only existed in shoe stores. Maybe the luthier trade needs some equally bespoke (but otherwise entirely useless) tool for measuring violin backs. The problem with the caliper is that is might actually be good for something else.

July 11, 2023, 1:00 AM · Paul - I get it. Violinists worry about fractions of a mm but violists think in inches...

July 11, 2023, 3:24 AM · There seems to be a lot of misunderstanding here about how the measurement is taken. First of all, the points used for determining back length are not on the highest points of the arching, and they are taken from the edge, which is not the lowest point, either. The amount that the arching changes the numbers is nowhere near what is being hypothesized, because the thought experiment is being conducted with improper assumptions. Violins don’t have flat plates, so there’s no reason that they ought to be treated as such in measuring them.

Caliper measurements are certainly useful, but the reality is that measuring tapes are much more practical. No one who sells violins is going to want to carry a giant caliper around when a small tape fits in a pocket and gives a number that you can actually take to the bank. Many buyers of violins often carry a tape along with them on trips to shops, and checking the back length is a part of deciding whether to make a purchase on the spot. When you’re dealing in violins, you often have to make decisions in moments, so what may seem like a small detail to some is one that makes or breaks a sale.

If you’re using a measurement system that doesn’t line up with what the majority of the violin world uses, it means you have to accept the risk that you may end up with some instruments that are rejected right off the bat because they’re long and some that are labeled as 7/8 because they run small. There is a market for 7/8 violins, but it’s not nearly as wide as that for “full-size” violins.

Edited: July 11, 2023, 8:10 AM · I certainly understand why luthier David Sora would find caliper measurements more useful, but as Rich Maxham points out, tape measurements are the convention among players and dealers. Buyers want to know the LOB by tape measurement to compare instruments.

I do disagree with Rich regarding instruments with longer backs inherently having darker tones than smaller fiddles because there are plenty of violins with LOBs under 360mm with dark tones. Arching and rib height also contribute to body volume. I think that violins over 360mm (in general) are harder to play for people with smaller hands without any inherent advantages over violins under 360mm, and therefore the market size for violins around 356+/-4mm is naturally larger.

Edited: July 11, 2023, 8:24 AM · As an incorrigible sceptic I don't buy the "harder to play" argument against larger violins either. People aren't all the same size (arm lengths must vary by at least 10cm across the adult population, finger lengths by a cm or two) so I fail to see why it has become the default assumption that one violin size fits (nearly) all.

Edited: July 11, 2023, 11:33 AM · Steve, If you were a small person or a young person stepping up from a three-quarter size to a full-size instrument, a smaller violin or even a seven-eighths size might be more comfortable to play.

There are no inherent advantages to larger violins over normal size violins. If there were, more people would make them and more people would would play them, but they don't because 356+/-4mm fiddles work very well for most players.

July 11, 2023, 8:13 PM · George,

I didn’t say longer instruments are inherently darker. I said they’re often more viola-like, and not all violas are so dark. It’s more about the voicing. A bright viola doesn’t necessarily sound like a violin. Arching and rib height are important factors in volume, which is why some people will adjust those things to counteract a longer back. But under normal circumstances, a longer body with average rib heights and moderate arching is likely to sound tubby.

Darkness is a different characteristic, and there are dark violins that aren’t large. I have violins from a family of makers that are darker than just about anything, and their back lengths are always under 360.

As to the feel in the hands, the back length can be compensated for by shortening the neck. Some viola makers do this so that players can use a larger, more voluminous body without having to deal with increased interval spacing.

Edited: July 12, 2023, 12:30 AM · Rich - you say "the back length can be compensated for by shortening the neck". Surely this will result in the same problem as I have with one of my longer violins, which is having to stretch the hand further to reach higher positions. When my thumb rests in the crook of the neck I expect my fingers to fall naturally in the fifth position. With my problem violin I'm a semitone flat which throws me rather badly in some repertoire.

July 12, 2023, 3:20 AM · Steve,

What you describe is a problem that can arise from using a shorter neck. There are workarounds for this, such as changing the position of the fingerboard or carving more out of the neck heel to give more room for the thumb. None of these are ideal solutions, but that’s the point I was trying to make in the first place—a body that’s too long can cause problems that aren’t easy to solve and are often just not worth the attempt. This is precisely the reason why so many shops don’t want the headache.

Edited: July 12, 2023, 7:14 AM · Rich, you're correct - you wrote "viola-like" and I said "darker," which is the tone quality that it is popularly assumed that fiddlers prefer. However, I have never heard a fiddle player say that they prefer a body length that is more "viola-like" unless it was for a 5-string violin.

Violas generally do have a darker tone quality than violins on the strings that they have in common. Small violas usually have taller ribs than violins to help achieve this.

I don't know about using non-standard neck lengths for violas, but a non-standard neck length on a violin is a much greater problem than a longer LOB for virtually any player. IMHO, a non-standard neck length is a defect that should be fixed, reset, or replaced to the standard length regardless of the LOB.

July 12, 2023, 9:54 AM · Rich - or you could leave the neck in its usual proportion to the body length and ask the player to extend their elbow about 1 degree more in first position. Seems like a small thing to ask.

July 12, 2023, 10:09 AM · Tape measures are useful to have but can be inaccurate. My mother had a good cloth one dating from about 1960 or earlier. I've bought a few on Amazon from China. The best are fibreglass nowadays(?) but some of the cheaper plastic ones can be a good 10% out. I compared them with a steel rule and threw the really bad one away.

July 12, 2023, 10:48 AM · Steel rules can be pretty out too. There was a batch made in India and sold by a big woodworking store a few decades ago that were awful.

July 12, 2023, 12:00 PM · Calipers can also be inaccurate. Not all of them are made to the same tolerances and one can easily come up with conflicting readings if the tool isn’t used properly or consistently placed in the same spot. A lot of people assume that, because calipers have dials or digital readouts, that they must be infallible. That’s not the case.

July 12, 2023, 3:34 PM · Steve wrote, "Violinists worry about fractions of a mm but violists think in inches... " It's taking every ounce of my restraint to avoid responding with "British humour."

July 13, 2023, 2:24 AM · Many a true word... I'm currently playing a 16.25" viola while in the past I've used a 17" and a 15.5" for long periods. Switching between them didn't bother me too much, but of course I probably never went above 5th position. For violinists 14" is fine but 14.25" is apparently too big.