Running Vest Sizing: Measure and Compare Between Sizes
How do you size a running vest? Use the current measurement chart for the exact model, then check the size with your normal layers, filled water containers and gear. Confirm that you can breathe deeply, move your arms and reach the pockets without forcing the closures. At a size boundary, follow any model-specific guidance and compare the two fits with the same load.
Start with the current chart for the exact model. If the manufacturer gives specific guidance for overlapping ranges, use it. Then compare the two sizes with the same kit and clothing.
ROOT5 running vest size chart: chest circumference
The current ROOT5 product page lists these chest ranges. Use its measurement instructions and check the live chart before ordering.
| ROOT5 size | Chest circumference, cm | Approximate inches |
|---|---|---|
| S | 78 to 90 | 30.7 to 35.4 |
| M | 90 to 102 | 35.4 to 40.2 |
| L | 102 to 115 | 40.2 to 45.3 |
| XL | 115 to 125 | 45.3 to 49.2 |
The endpoints overlap. Record the measurement rather than rounding it to fit one range. Our published ROOT5 runner feedback recommends sizing up between sizes; still compare the loaded fit and confirm model-specific guidance if you are unsure. This table applies to ROOT5. Use the separate current instructions for ROOT8 or ROOT18.
ROOT5 listing checked October 1, 2026. Inch values are approximate.
Measure for the model you are considering
- Use a flexible tape and follow the measurement location shown on the product page. Keep the tape level and comfortably close, without pulling it tight.
- Compare the result with the current chart for that exact model. Check the units and whether you fall near a boundary.
- Wear the shirt or layer you will normally run in when trying the vest. Adjust the sternum and side closures within their normal range.
The ROOT5 product page publishes a chest-circumference chart for its S, M, L and XL variants. Check that live chart before ordering. The ROOT8 and ROOT18 are different pack designs; do not assume that the same letter, measurement range or adjustment applies across all three. If the listing does not give the measurement you need, ask LECAMO for the model-specific guidance before buying.
Record the measurement the chart asks for
Read the measuring instructions before reaching for the tape. A chart may ask for a particular body measurement; a familiar shirt size is not a substitute.
Keep the tape in the specified position and record the result. Wear the layer used in the fitting instructions. If your usual running clothing differs, include that in the practical comparison too.
REI’s hydration vest guide recommends using the manufacturer’s sizing guidance and evaluating the vest with weight inside it.
Use one load for both sizes
Fill your intended water containers and pack your phone, food and usual spare layer. Use this same load when trying each size.
An empty small size and a loaded larger size are not a useful comparison. They change two things at once. Keep the load constant so you can identify the effect of the size itself.
If you are still deciding what the vest needs to hold, review the capacity guide before treating volume and fit as one decision.
Check available adjustment
Follow the adjustment instructions and notice how much useful adjustment remains. Record whether a closure has reached its limit and whether the vest still feels loose or uncomfortable.
Avoid trying to correct every problem with tighter straps. A bottle pressing in the wrong place, a low edge catching your waist or an awkward shoulder shape may require a different configuration or cut.
Make normal arm movements, walk and bend forward. Persistent pressure is a reason to stop and reassess.
Compare access and the lower edge
Reach for the same pocket in each size while stationary. Check whether the phone closes inside its compartment and whether you can remove food without shifting the whole vest.
Raise your arms and bend to tie a shoe. Note the position of the lower edge. These checks add information that a circumference measurement alone cannot provide.
The women’s loaded fit guide offers a closer look at chest comfort and torso length.
Repeat after reducing the water load
Remove some water and repeat the movement check. Note whether adjustment remains comfortable and practical. Use our bounce troubleshooting guide if movement appears only after the load changes.
For LECAMO, select from the exact model’s current chart and your comparison notes. Choose the size that works with your actual kit rather than applying a rule from a different brand or garment.
What testers found about sizing in practice
Our published runner reviews describe four runners’ experiences with gifted ROOT5 packs. One larger runner described an initially snug fit and later reported that it felt good in use. That report does not give a chest measurement or establish a size boundary. The page’s advice to size up between sizes is guidance to consider alongside the current chart and your loaded comparison. Read the runner feedback and gifted-product disclosure before using the notes to inform your choice.
Running vest sizing questions
Should a running vest fit tightly?
Look for a close, comfortable loaded fit with usable adjustment. If taking a deep breath or reaching a pocket feels restricted, reassess the size, cut or permitted adjustment. REI’s fit guidance also recommends manufacturer-specific measurements and a loaded fitting.
Should I change size when one flask bounces?
First identify whether the flask moves in its pocket or the whole vest shifts. Check compatible flask shape and intended retention before changing body size. Use the bounce diagnosis for that distinction.
What if the measurements match but an edge rubs?
Record the contact location, clothing and load. Compare bottle position and the actual cut rather than relying on circumference alone. The contact-point fitting table helps separate those checks.