Measuring Sight Radius
Sight radius is the distance from your peep sight to the front sight housing pin. Getting this right is critical — an error of even ½ inch will throw off every mark on your tape.
What to Measure
Measure from the centre of your peep hole to the centre of your sight housing pin (the hole the pin passes through in the housing). This is the aperture-to-aperture distance, not the physical distance to the bow riser.
How to Measure
- Draw the bow to full draw if possible — this is the position you'll be at when aiming, and the sight and peep are in their natural orientation.
- If you can't draw, hold the bow at full extension and measure while someone else assists.
- Use a flexible tape measure or a long ruler along the string/arrow line. Don't measure at an angle.
- Measure multiple times and average the result.
Tip: If you have a non-adjustable peep or a fixed rear aperture, the measurement is straightforward. If your sight slides on a bar, make sure to measure with it set to roughly the middle of its travel — the position it'll most often be at during hunting distances.
Typical Values
Most compound setups fall in the 6–12 inch range for sight radius. Longer draw lengths and longer sight bars push this higher. Short axle-to-axle bows with compact sight bars tend to be on the shorter end.
Note: If your sight slides along a rail (as most hunting sights do), your effective sight radius changes slightly as the sight moves. The value you enter should be your approximate mid-range position. The tape accounts for the rest.