How much weight can strut channel support?
There is no single number, and any page that hands you one is guessing. Strut channel capacity is published part by part by the manufacturer that made it, and it moves with the profile depth, the steel gauge, the span between supports, how the load sits on the run, and the deflection your specification will accept.
That sounds like a dodge until you put two catalogs side by side. Two channels that both read "1-5/8 inch, 12 gauge" on a submittal can come off different lines with different steel and different lip geometry, and their published values do not match. The table that applies to your job is the one printed by the company whose part number goes on the purchase order. Unistrut and Eaton B-Line both publish load data publicly, and most other makers do too.
What actually sets the capacity?
Profile depth does the most work. A deeper channel puts more material away from the neutral axis, so it resists bending better than a shallow channel of the same gauge. Welded back-to-back and combination sections go further again.
Steel gauge comes next. A lower gauge number means thicker steel, and thicker steel carries more and sags less. What that is worth on your run is the subject of 12 gauge vs 14 gauge strut channel, and it still comes out of the table rather than out of a ratio.
Span is where people get burned. Capacity drops off as the distance between supports grows, and it drops faster than most people expect, because bending and deflection do not scale with span the same way. Adding one more support to a run is often cheaper than moving the whole run up a gauge.
How the load sits matters as much as what it weighs. Published tables are almost always uniform load, meaning weight spread evenly along the span. The same total weight hung from a single point in the middle of that span works the channel harder. Use the manufacturer's conversion for that, not a rule of thumb somebody remembers from a jobsite.
End conditions change the answer. A channel simply supported at both ends of one span behaves differently from the same channel running continuously across three or four supports, and differently again from a cantilever hanging past the last support. Every table states the condition it assumes.
Deflection is the quiet governor. On longer spans the channel reaches the sag your spec allows well before it reaches anything close to a strength limit. That is why a table can show a load at a span and still be the wrong pick for a run where a conduit cannot move or a piece of equipment has to stay level.
Finish does not change the published number for a new part, but corrosion removes section over time, and lost section is lost capacity. Pick the finish for the environment the run lives in.
How do you read a strut load table?
Read the footnotes before the grid. They carry the assumptions that decide whether the number applies to you at all.
Then check five things. That the table covers the exact series, part number, and gauge you are buying, not just the family. That total load on the span and load per foot are not getting confused, because they are different numbers. That the support condition matches your run. That the deflection listed alongside the load is one your specification can live with. And whether a safety factor is already inside the published value, because guessing wrong there goes in the unsafe direction.
Strut is a cold-formed steel product, and cold-formed steel member design in North America is governed by AISI S100. You do not need to work through that specification to use a table. You do need to know the table is the manufacturer's engineering for its own product, not a general property of steel channel.
What the table does not cover
The channel is often not the weak link. The bolt, the strut nut, the anchor into the deck, and the structure overhead all have their own ratings, and on plenty of runs one of those governs first. Anchors into concrete are a separate calculation with their own failure modes. A table also says nothing about load hung off one side of the channel, which adds torsion, or about anything that starts, stops, swings, or vibrates.
When do you stop reading tables and call an engineer?
When the run is over people, over equipment that cannot be replaced, or part of a fire, life-safety, or process-critical system. When seismic or wind bracing is in play. When the authority having jurisdiction wants a stamp. And when the installation does not match the assumptions any table you can find was built on. An hour with a licensed structural or professional engineer beats another afternoon of catalog reading.
If you want to walk the same variables in order first, the Strut Channel Support Configurator steps through profile, gauge, finish, and a span-and-load sanity check, then hands you a parts list. The load figures in it are illustrative assumptions, not verified engineering data, so use it to sanity-check a configuration and confirm every value against the manufacturer's published load tables and a qualified engineer. It sits in the Rethink tool catalog. The next question most people ask is what sets the maximum span between supports.