Tension a hot chain by feel and it will be too tight by the time the saw is cold. The reading itself was wrong.

Do not make the final adjustment on a hot chain

The core of the subject. A hot chain has expanded and therefore reads slack, and it contracts as it cools, so a tension that feels right at the end of a cutting session will be tighter than intended once the saw is cold. Guidance describes it as a false reading rather than a judgment error: hot components provide false tension readings due to thermal expansion of metal parts, leading to over-tightening when cooled. Another source states directly that the final adjustment should not be made while the chain is very hot, and a supplier’s pro tip notes that many chain loosening problems happen precisely because people tension while hot, recommending a cold or slightly warm chain for the most accurate result. Adjust during the session if you must, and set it properly once it has cooled.

A new chain needs retensioning after a minute or two of cutting

Manufacturer guidance rather than folklore. Husqvarna’s support documentation tells owners plainly that new or recently adjusted chains can stretch quickly and to check and adjust tension again after one to two minutes of cutting. The reason is that the links and rivets have not fully seated against each other, and cutting loads settle them, which elongates the chain slightly. Sources give different intervals for how long the break-in lasts, from checks every five to ten minutes for the first few hours, to every fifteen to twenty minutes until it stabilizes, so the safe reading is very frequently at first. And a useful detail: break a new chain in on softwood, since it puts less stress on the chain while everything seats.

A chain that keeps loosening is usually telling you about oil

The most valuable reframe here, because it stops an endless loop. Insufficient bar and chain oil increases friction between the drive links, the guide bar rails, the nose sprocket and the drive sprocket, and the resulting heat accelerates wear and causes the chain to require repeated adjustment. The symptom set is specific and worth memorizing: a chain running without sufficient lubrication may become hot, stiff, discolored, or difficult to pull by hand. And the conclusion is stated as a stopping rule, that repeated retensioning will not correct the problem until oil flow is restored. A practitioner traces the same loop from the other end, noting that failing to clean the bar stops oil reaching the chain, which heats and stretches it, and wears the drive sprocket from the same root cause.

Lift the bar tip while you tighten the nuts

A small step that changes the result and is the easiest thing on this page to skip. Every source describes it: while tightening the bar nuts, lift the tip of the guide bar upward, because letting it sag introduces slack into the chain. The bar can move slightly within its mounting while the nuts are loose, so whatever position it settles into is the position the tension gets locked at. Lifting the nose takes the sag out of the equation and is the difference between a tension you measured and a tension you happened to get. Firm normal wrench pressure on the nuts, not maximum effort.

The engine is off. There is no version of this done running

Stated because the temptation exists when you are checking tension repeatedly through a day and the saw is right there. All chainsaw manufacturers explicitly prohibit tension adjustments with a running engine in their safety manuals and training materials, and the reason needs no elaboration. The related habit is worth building deliberately: check the tension whenever you refuel or add oil, which attaches the check to a stop you were already making with the engine already off. That way the frequent checking a new chain needs does not become a reason to take shortcuts.

Know what correct feels like, from more than one angle

Sources describe the target in several complementary ways and having all of them is better than having one. Husqvarna describe being able to lift the chain slightly at the center of the bar and see only a small portion of the drive links, without pulling them fully out of the groove. Others give roughly three to four millimeters, or about an eighth of an inch, of lift at the midpoint. A correctly tensioned chain snaps back when released rather than staying lifted. And it should still be possible to pull the chain around the bar by hand while wearing gloves, which is the check that catches over-tightening, since a chain that binds is as wrong as one that sags.

Three things that are not tension problems at all

Worth recognizing so that the answer stops being another quarter turn. First, a permanently stretched chain: if a chain has been retensioned multiple times and still will not hold, it may simply be overstretched, and chains have a lifespan after which they cannot be fixed. Second, a worn bar groove, where the safety consequence is named directly, that a worn bar is a hazard because the chain is more likely to slip and cause kickback. Third, mismatched components, and this one is more common than people expect: many after-sales complaints are caused by mismatched chains, bars and sprockets rather than engine failure, and a replacement chain must match more than the nominal guide bar length. Getting the pitch and gauge right matters as much as the length.

If tension changes as you rotate the chain, suspect the sprocket

A practitioner diagnostic that is genuinely non-obvious and worth having. If a chain feels tight at one point in its travel and looser half a turn later, that is not a chain problem. A forum explanation identifies the likely cause: the bar nose sprocket may have its hole machined slightly off center, so it effectively sticks out farther in one orientation than the other, tightening and loosening the chain as it turns. The test follows from the explanation, which is whether the tension variation repeats on the sprocket’s rotation rather than the chain’s. And a related rule: do not reuse a chain with damaged drive links, stiff joints, cracked components or excessive wear, and inspect any chain carefully that has jumped off several times before putting it back on.