Parallax setting
Fixed or Adjustable Parallax: Do You Actually Need It?
Quick answer
For big game shooting inside 300 yards, a fixed 100 yard parallax setting produces less error than your own eye position does, so adjustable parallax is a precision-rimfire and small-target upgrade rather than a general one. With a 100 yard fixed setting and a tenth of an inch of eye offset, a 300 yard target carries only about 0.2 inches of available error.
Vortex Diamondback 3-9x40 Riflescope, Dead-Hold BDC Reticle
$249.00 Full specificationsParallax factory set at 100 yards, the standard convention for a centrefire hunting scope, with no adjustment mechanism to add cost or another dial to manage in the field.
Best for: the buy-once hunting scope at a sensible price
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Athlon Argos BTR GEN3 6-24x50 Riflescope, APRS11 FFP IR MIL Reticle
$379.99 Full specificationsSide focus parallax adjustable from close range out past 500 yards, built for a scope used on small or distant targets where the fixed 100 yard convention would leave real error on the table.
Best for: a mil-reticle precision build on a budget
Check price on AmazonA fixed parallax scope has its internal lens set at the factory to remove parallax error at one distance, almost always 100 yards on a centrefire hunting scope, and left there permanently. An adjustable parallax scope, whether by side focus or an adjustable objective ring, lets you move that same lens to match whatever distance you are actually shooting.
The honest question is not which one removes parallax more completely. It is whether the parallax error a fixed setting leaves behind at other distances is large enough to matter next to every other error already in the shot. For most big game hunting, it is not.
These figures are researched from published parallax error formulas and manufacturer fixed parallax conventions, not from a side by side field comparison of these two scopes.
What parallax error actually costs you at distance
The working
Parallax error scales with how far the target distance is from the parallax setting, and with how far your eye sits off the optical axis. A small eye offset at a target close to the parallax setting produces a small error. The same offset at a target far from the setting produces more.
Manufacturer fixed parallax conventions and published parallax error formulas, not a measurement of these two specific scopes.
Take a fixed parallax scope set at 100 yards, the standard convention for a centrefire hunting scope, and a realistic tenth of an inch of eye offset from the optical centre, which is closer to typical field shooting than a bench rest position gives.
A 300 yard target through a 100 yard fixed parallax setting carries about 0.2 inches of available error at a tenth of an inch of eye offset, smaller than the group size of most hunting rifles and loads.
Sourced figure
| Target distance | Distance from parallax setting | Approximate error at 0.1 in eye offset |
|---|---|---|
| 100 yd | 0 yd | 0 in, exactly at the parallax setting |
| 200 yd | 100 yd | About 0.1 in |
| 300 yd | 200 yd | About 0.2 in |
Error grows roughly in proportion to how far the target sits from the parallax setting. At the distances most big game hunting happens, a small, consistent eye offset produces an error well inside normal group size.
Why this makes adjustable parallax a precision and small-target feature
A 0.2 inch error at 300 yards is not a meaningful contributor to a miss on a deer sized vital zone, which is measured in many inches rather than fractions of one. It is a meaningful contributor on a target that is itself only a fraction of an inch across, which is exactly the situation precision rimfire shooters and small-bore competitors face, and exactly why adjustable parallax is close to universal on scopes built for that discipline. The same error that is invisible on a big game hunt is a real fraction of the target on a rimfire steel challenge at 50 yards.
Long range centrefire shooting past a few hundred yards is the other case where adjustable parallax earns its keep, not because the error at any one distance grows dramatically, but because the range itself varies shot to shot and a fixed 100 yard setting leaves an increasing, if still modest, error at every distance past it. See exactly how this plays out at a 100 yard parallax setting against a 300 yard target and at a 50 yard parallax setting against a 50 yard target for the same arithmetic worked at other combinations.
Where adjustable parallax is worth paying for anyway
Precision, cost, and reach all point the same direction: a hunter shooting big game inside 300 yards with a rifle they hold steadily loses very little by buying a fixed parallax scope, and gains a simpler, usually less expensive optic with one fewer dial to manage under field conditions. A rimfire competitor chasing a target the size of a coin, or a long range shooter whose distances genuinely vary widely and unpredictably, is solving a different problem, and for them the small error a fixed setting leaves behind is worth removing.
Sources
- Vortex Optics published specifications
- Athlon Optics published specifications
- Parallax error, standard published optical formula
Frequently asked questions
Do I need adjustable parallax for deer hunting?
Usually not. Inside 300 yards, a fixed 100 yard parallax setting produces roughly 0.2 inches of error at a realistic eye offset, which is small next to a deer sized vital zone and normal group size. Adjustable parallax becomes worthwhile past those distances or when shooting at targets small enough that a fraction of an inch actually matters.
What distance is a fixed parallax scope usually set at?
100 yards on the great majority of centrefire hunting scopes, which is a manufacturer convention rather than a published standard. Rimfire and airgun scopes commonly use a shorter fixed setting, often 50 yards, matching the shorter distances those platforms are typically used at. Always check the specific scope's specifications rather than assuming 100 yards applies.
Why do precision rimfire shooters need adjustable parallax?
Because their targets are often only a fraction of an inch across, so an error that is invisible on a deer sized target becomes a meaningful fraction of a small rimfire target. Adjustable parallax removes that error at whatever exact distance the shooter is engaging, which matters far more when the target itself leaves little margin.
Does eye position matter more or less than parallax setting?
They work together. Parallax error only appears when your eye sits off the optical centre of the scope, so a shooter with a very consistent, centred eye position sees almost no parallax error even far from the fixed setting. A shooter with inconsistent head position introduces error even on an adjustable parallax scope if it is dialled incorrectly.
Is adjustable parallax worth the extra cost for long range shooting?
Often yes, because long range shooting means the target distance varies unpredictably shot to shot, and a fixed 100 yard setting leaves a small but growing error at every distance past it. Combined with the reach benefits of side focus, adjustable parallax is one of the more justified upgrades on a dedicated long range scope.
Can a fixed parallax scope still be accurate at 300 yards?
Yes. The error a 100 yard fixed setting leaves at 300 yards, roughly 0.2 inches at a realistic eye offset, is smaller than the group size of most hunting rifles and loads. Accuracy at that distance is governed far more by the rifle, the load and the shooter than by the small residual parallax error a fixed setting leaves behind.
Researched, not professional advice. This page is compiled from published manufacturer specifications, published optical and ballistic formulas, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are shooter convention rather than sourced numbers, and they are labelled that way wherever they appear. Ballistic figures come from a point mass model using the ballistic coefficient the maker publishes, so treat them as a starting point and confirm them on paper at a measured distance. Confirm your firearm is unloaded with the action open before you mount, level, torque or bore sight anything. Verify a zero only on a supervised range or a safe, legal backstop, know what lies beyond your target, and follow the law where you hunt and shoot, including rules on land access and permitted cartridges.