In my hard sci-fi settings, there is an advanced Type II Civilization, that are progressing toward Type III Civilization (yes, I am referring to Kardashev Scale). They are sprawling across the galaxy with relativistic ships, generational ships, and perhaps counless unmanned Von Neumann probes (but there is no faster than light travel). Most are under the rule of benevolent (or even malevolent) AI Gods, that also contributes in development of large scale projects and scientific advancements. Along with it are plenty of megastructures on astronomical scales, including Dyson Swarms and many esoteric megastructures we might not be able to comprehend their functions at all.
One of the advancement they achieve is the introduction of economically feasible stargates. Apparently the AI Gods managed to solve most technical issues with wormholes, including development of stargates with sufficiently small negative mass requirements, and of significant size that most starships can pass through. They are connecting major star systems and clusters, and so many developed systems possess stargates of enormous size, up to several kilometers wide, but typically stargates are about less than kilometer in size.
The stargate is supposedly based on Thorne-Morris wormhole, modified slightly by Kuhfittig to allow arbitrarily small requirements of exotic matter. However (call me lazy but...) I have no idea what the equations inside those papers mean.
For my worldbuilding purpose, I want to know how to calculate the gate's mass, given its throat radius, so we comes with this question: how to calculate the mass of a stargate, given desired radius is known?
The question seeks answers that could devise a wormhole given certain radius, that requires arbitrarily small amount of exotic matter. Hopefully, for a gate of some kilometers big, its mass is around the same mass as Earth's moon, and ideally it should be less than Earth-mass.
Answers that describe the behavior and structure of said gate is weighed up. Especially, on stability (for example, mass limit of objects that can safely traverse a gate of certain radius, or when the gate collapsed, what would happen to the exotic matter, and would it create a black hole of what size?), and at what radius did the exotic mass distribution ceases (see Miscellaneous section).
Answers that are based on the cited papers and sources are preferred, but if there is any other paper that could produce gates with more desirable properties (smaller mass for a given radius is an example, or perhaps without the need of exotic matter!), they are too, appreciated.
Regarding traversable wormhole, I consider this to be the standard. So answers must produce wormholes that are symmetrical and static, containing a throat that connects two asymptotically flat regions of spacetime, no event horizon, bearable tidal forces, reasonable transit time, stable against perturbations, and feasible mass requirements.
For the purpose of this question, assume that wormhole is not impossible, and exotic matter of some form can be obtained. Also, to solve problems with the existence of wormholes implies possibility of time travel, assume that it is impossible to arrange wormholes into time machine, and any wormholes that could lead to violation of causality would be unstable and collapse (in another words, chronology protection conjecture is assumed true).
Probably worth mentioning, but I consider that the stargate in question is Medium-Exotic-Region Wormhole, or even Small-Exotic-Region Wormhole according to this answer. I don't know whether or not it will change the property of said wormhole, but I read somewhere (I can't find the link) that extending the exotic region into larger volume of space equals increased mass. By that logic I suspected that smaller region of exotic matter means smaller mass. And because the answer stated that if the exotic matter is restricted so closely to the throat, it is "absurdly benign", I think, it is a safer bet that the exotic matter would be loosely restricted to the throat (which, is also how Kuhfittig approached the feasibility of a wormhole with arbitrarily small exotic requirements of exotic matter, in the cited paper).
About the mass of a wormhole, as first mentioned by Dubukay on sandbox, I discovered that the mass of a wormhole is its ADM Mass. Perhaps this is also unrelated, but I discovered this answer, that explained that a wormhole gains mass of the incoming object in the entrance mouth, and lost equivalent mass of the out-coming object from the exit mouth.
Edit 1 (21 January 2019)
The title is edited so that now it focus to the way to calculate its mass. And to clarify comments about whether nor not the hard science tag is eligible for this question, I use this tag under the need for a question backed up with equations, and relevant theories, preferably from peer-reviewed scientific papers. The basis of my argument is on this quote from tag info of "hard-science" (here):
Ideally, answers should be backed up by equations, relevant theories, and citations where possible - arXiv can be quite good for citations, though Wikipedia is usually OK too.
On comment about whether I could understand the math behind this question, I have it outlined above that the answer I seek must explain how to calculate the mass of said wormhole by knowing its radius, a qualification of model accepted (the less mass for a given radius, the better), and a requirement to state which units used (geometrized units or in SI, where SI units or conversion to SI units is preferable). All of those requirements ensures that all answers boils down to how to calculate the gate mass given only its throat radius.
I believe with all of those requirements, the answer is not impossible, based on known (albeit speculative) current theoretical physics. This is something I could not get from just science-based tag.
Edit 2 (28 January 2019)
I rephrase certain parts of the question and considerations to reflect corrections provided by the commenters.