A running vest that fits properly feels like a natural extension of your body—you barely notice it's there even after hours on the trail. A poorly fitting vest, on the other hand, bounces, chafes, restricts breathing, and can turn an otherwise enjoyable run into an uncomfortable ordeal. Getting the fit right is arguably more important than any other feature when choosing a running vest.
This guide walks you through everything you need to know about sizing and fitting a running vest, from taking accurate measurements to fine-tuning adjustments for the perfect fit.
Understanding Running Vest Sizing
Running vest sizing differs significantly from regular clothing sizes. Most brands use chest circumference as the primary measurement, but sizing scales vary considerably between manufacturers. A medium in one brand might fit like a small in another, so never assume your size will be consistent across different vests.
Additionally, running vests are designed to fit more snugly than everyday clothing. The goal is a close, body-hugging fit that minimises bounce and movement. If you typically wear a medium t-shirt, you might find yourself between sizes in running vests, often needing to go down a size for the right fit.
Taking Your Measurements
Before shopping for a running vest, take these key measurements using a flexible tape measure:
Chest Circumference
The most important measurement. Wrap the tape measure around the fullest part of your chest, typically across the nipple line for men and across the fullest part of the bust for women. Keep the tape parallel to the ground and snug but not tight. Take the measurement while exhaling normally.
Torso Length
Some vests come in different torso lengths. Measure from the bony prominence at the base of your neck (where your neck meets your shoulders) down to the top of your hip bone on the side of your body. This is particularly relevant for women's vests, which often account for shorter torso lengths.
Take measurements wearing the type of clothing you'll typically run in. A thin singlet fits differently than a winter base layer, and this can affect which vest size works best for you.
Consulting Size Charts
Every reputable running vest brand publishes size charts, and consulting these is essential. Don't rely on your typical clothing size—always check the specific chest measurements for each size.
If you fall between sizes, consider these factors:
- Running style: For racing and fast running, size down for a tighter fit that minimises bounce
- Layering needs: If you'll often wear thick layers underneath, sizing up may be appropriate
- Body composition changes: Training for ultras? You might lose weight during long events; training through winter, you might carry slightly more
- Brand recommendations: Some brands explicitly suggest sizing up or down for certain body types
Trying On a Running Vest
Whenever possible, try vests on before purchasing. Here's how to assess fit properly:
Initial Fit Check
Put on the vest without adjusting any straps. It should feel snug across your chest and back without being restrictive. You should be able to take a full, deep breath without feeling constricted. The vest should sit flat against your body without gaps or bunching.
Movement Test
Jog on the spot, jump up and down, and swing your arms through a full running motion. A well-fitting vest should move with your body, not independently. Watch and feel for:
- Vertical bounce—the vest should stay in place, not ride up
- Lateral shifting—it shouldn't swing side to side
- Arm restriction—you should have full range of motion
- Pressure points—no areas should dig in or feel uncomfortably tight
Load Test
A vest that feels perfect empty may fit differently when loaded. Ask if you can add soft flasks or weights to simulate a loaded vest, then repeat the movement test. Pay particular attention to how the front pockets sit when filled—they shouldn't swing or pull the vest forward.
- Snug but not restrictive across the chest
- No gaps between vest and body
- Front pockets accessible without excessive reaching
- Sternum straps sit comfortably without riding up to collarbone or down to stomach
- Shoulder straps don't dig into neck or slide off shoulders
- Back panel sits flat without bunching
Understanding Adjustment Systems
Modern running vests include various adjustment points that allow fine-tuning of fit. Understanding these systems helps you dial in the perfect fit.
Sternum Straps
Most vests have one or two sternum straps that connect the front panels across your chest. These are your primary adjustment for preventing bounce and securing the vest. Sternum straps should be tight enough to hold the vest in place but loose enough that you can breathe deeply without restriction. Many runners find positioning one strap above the bust/pectoral area and one below works well.
Side Adjusters
Premium vests often include bungee cords or straps along the sides that allow you to compress the back panel closer to your body. These are particularly useful for cinching down when carrying lighter loads.
Shoulder Adjustments
Some vests allow adjustment of how the front panels attach to the shoulder straps. This affects how high or low the front pockets sit. Experiment to find a position where pocket openings are easily accessible while running.
Gender-Specific Considerations
Women and men have different body shapes, and running vest designs increasingly reflect this. Women's-specific vests account for narrower shoulders, shorter torsos, and different chest shapes.
For Women
Look for vests designed with women's anatomy in mind. Key features include:
- Narrower shoulder straps positioned to avoid interference with sports bra straps
- Front pockets shaped and positioned to accommodate different chest sizes
- Shorter back panels proportioned for typically shorter female torsos
- Sternum straps that can be positioned above or below the bust
Many women find unisex or men's vests uncomfortable because the shoulder straps are too wide and front pocket placement doesn't work with their body shape.
For Men
Men's vests typically assume broader shoulders and longer torsos. If you have a smaller build, consider trying women's or unisex options, as these may provide a better fit than the smallest men's size.
Common Fit Problems and Solutions
Vest Rides Up
Usually indicates the vest is too large or straps aren't tight enough. Try sizing down or tightening sternum and side straps. Some vests also have lower attachment points that help anchor the vest in place.
Chafing on Shoulders or Under Arms
Often caused by straps that are too loose, allowing friction during movement. Tighten adjustable straps. If specific seams or edges cause irritation, try applying anti-chafe balm to affected areas.
Bouncing Front Pockets
Typically occurs when soft flasks are too heavy for the vest's front panel design, or straps aren't tight enough. Ensure sternum straps are snug and consider using lighter flasks. Some runners add additional compression by wearing a race belt over the vest's lower edge.
A vest that causes problems on a short test run will cause worse problems on a long one. Never race in a vest you haven't thoroughly tested during training. Use long runs to identify and resolve any fit issues before race day.
Difficulty Breathing
The vest is too small or straps are overtightened. You should always be able to take a full, deep breath. If not, loosen straps or try the next size up.
Hard to Access Pockets
Pocket position may not suit your body shape. Try adjusting shoulder straps if possible, or consider a different vest design. Some vests have front pockets positioned higher or lower than others.
Testing Your Fit in Training
Once you've selected and adjusted your vest, put it through progressively longer and more challenging tests:
- Short easy run (30-45 min): Identify any obvious problems with bounce, chafe points, or restrictions
- Medium run (60-90 min): Issues often emerge as runs get longer and sweat accumulates
- Long run (2+ hours): The true test—simulate race conditions with full load
- Technical terrain: Test on trails similar to your goal event to ensure stability on varied terrain
After each test, note any problems and make adjustments. Consider marking your optimal strap positions with a marker so you can quickly return to your preferred settings.
When to Size Up or Down
Sometimes the right decision is to exchange for a different size. Consider sizing up if: you can't take a full breath, shoulder straps dig into your neck, or there's no room for any layering. Consider sizing down if: there are gaps between the vest and your body, the vest rides up during movement, or the shoulder straps slide off your shoulders.
A well-fitting running vest is worth the effort to find. Take your time with sizing and fitting, test thoroughly during training, and don't hesitate to try different brands if your current vest isn't working. The right vest should be comfortable enough that you forget it's there, allowing you to focus entirely on the joy of running.