A key difference between a seed factory and other production systems is self-expansion through replication, diversification, and scaling. So one group of useful measurements are for how much it can grow.

• Closure

An ideal self-replicating factory would be able to copy all its own parts, plus make useful products. Human-built systems are less than ideal, so we would like a way to measure a factory which can only copy some of its parts. In mathematics, a Closed Set is "a set that includes all the values obtained by application of a given operation to its members". Past discussions of replicating systems have used the term Closure to mean the outputs of the factory include all the parts which are required for it's own operation. Closure is also related to the idea of "closing the loop", where the output from a process loops back on a flow diagram to become a production input, namely the equipment to operate the process. For replication, closure only counts the factory itself. We can generalize it to include the factory and the products it makes. A Closure Ratio, CR, is then the quantity of outputs the factory can make, divided by the total quantity of that item used in the system itself. For example, using parts count of the factory as the item to measure:

${\displaystyle CR(parts)={\frac {N(produced)}{N(total)}}}$,

where N(total) is the total number of parts from which the factory is made, and N(produced) is how many of those parts it can make itself as outputs. You can measure closure ratios by mass, cost, parts count, quantity of design data, and other variables. So CR(mass) = 0.98 means the system can produce 98% of it's own parts by mass, and the remaining 2% must be supplied from elsewhere to make a complete copy. We can also measure the closure for end products other than the factory, CR_ep. This is the fraction of the end products made internally by the factory vs. parts and materials supplied from elsewhere. For example, a local computer shop which assembles them for customers, but does not make any of the parts themselves, would have 0% product closure. Finally, we can measure the closure ratio for a factory and all its products combined, CR_all. Both end product and combined factory + product ratios can be measured by mass, cost, and the other variables noted previously.

Calculating closure ratios for existing factories and products is a straightforward counting or measuring process. Analyzing potential closure ratios for a future self-expanding system is more complex. This follows a step-wise process working backwards from the end products to whatever equipment you start with. For a completely new seed factory, you start with no equipment - the starter set is supplied from elsewhere.

The first step is to identify which machines and processes you need to make the end products. From that you can identify which equipment you do not already have in place. For the missing ones you can further determine how much of them you can make internally with current equipment. Eventually you trace everything back to parts and materials you can make, or to those you can't. The ratio of internal make to end output is then your closure ratio for those products. In doing such an analysis, what would otherwise be a waste product from one process should be considered for recycling into another process. When you consider the factory itself as the end product, then the closure ratio measures the ability of the factory to replicate itself.

If you try to reach 100% closure in a self expanding system, in theory you can reach some set of starting machines that can make all the later ones plus copies of themselves. We know our entire industrial civilization can do this. All our current equipment traces back to previous generations of equipment and raw materials, and we can still make copies of the oldest and simplest tools. In principle a smaller set than all of civilization, consisting of at least one machine of each type, should also be able to fully copy itself. In practice, a few processes, like making computer chips, are difficult and expensive to do in small quantities. Others processes require rare materials, or are done so infrequently, that it does not make economic sense to have your own equipment to do them. The few previous studies on this kind of closed loop production found around 1-2% of the total items were not practical to self-make, or in other words 98-99% closure. Still, having to buy or import 1-2% of your parts and materials is a great improvement over the levels found in current factories.

• Output Range

A useful factory is able to make other outputs besides copies of itself. An Output Range, OR, for any factory can be defined by the range of possible outputs relative to the same parameter for the factory itself. So a 200% output range by mass means the list of possible outputs has twice the mass of the factory. This is calculated by counting one copy of each output. Most factories are intended to produce many copies of the product, but that is a measure of total output, and not the range in terms of variety of products. In the case of continuously produced materials, like coils of steel sheet, one copy is a deliverable load. Like closure, output range can be measured in terms of mass, cost, parts count, design data, and other parameters.

When the output range includes some parts of the factory itself, then OR by mass can be expressed as

${\displaystyle OR(mass)=CR(mass)+EP(mass)}$,

where OR(mass) is the mass of the total range of outputs, CR(mass) is the closure ratio by mass, i.e. the mass of its own parts it can output, and EP(mass) is the mass of all the other end products it can make. Traditional factories which make none of their own parts would have CR(mass) = 0, and EP(mass) > 0. While traditional factories tend to have low closure ratios they are often not zero. For example, cement and steel plants both typically use some cement and steel in their construction, and an electronics factory typically uses some electronics in its own operation. Seed factories are just intentionally designed to have much higher levels of closure. The output range of a traditional factory may be quite low. For example, the mass of an automobile is small compared to the mass of the auto assembly plant where it is made. A semiconductor foundry is quite large compared to the chips it produces. This is often the result of high levels of specialization and mass production at the expense of product flexibility. Self-expanding factories with programmable smart tools are more able to vary their outputs, by changing the software files for what parts to make, and then what products to assemble them into. So they can reach high output ranges.

• Expansion Range

Output range refers to all the outputs the factory can make. Expansion Range, ER, refers to the set of outputs which can be used to expand the factory, relative to the set of which it is made. So if a factory uses 8 production processes, and can produce parts for 4 new ones, it would have a 50% expansion range in process count. Measures for expansion range can use mass, parts count, number of materials used, or other quantities, in addition to process count. For example, we can write the formula

${\displaystyle ER(parts)={\frac {N(expansion\ parts)}{N(factory\ parts)}}}$,

where ER(parts) is the expansion range in parts count, N(expansion parts) is the number of new parts to expand the factory, and N(factory parts) is the number of parts in the current factory. A factory which can copy all it's own parts, but not make any new parts for different equipment, would then have CR(parts) = 100% and ER(parts) = 0%. This is actually an unlikely situation in the real world, but for now we are just trying to explain the types of measures.

The expansion range can vary with the growth of a self-expanding factory. It may be low at the seed stage, where only a few starter set machines area available, and can only produce a few types of new items. It may then increase as the factory grows and can make more types of materials and parts, and decrease again as it reaches practical limits in the types of materials and processes it can use. How the expansion range varies in a growing factory is a new area of study, and not well understood at present.

Civilization as a whole has a CR > 100%, and an ER significantly > 0%. Every existing production machine was made somewhere, and can therefore be copied simply by making another one the same way. So civilization can copy all its parts. The constantly growing range of products across time shows that existing equipment can make new equipment that didn't exist before. This proves by example that high levels of closure and expansion are possible. The design challenge for a seed factory is to reach high levels of these measures with a much smaller starter set than what all of civilization uses.