One of the most important decisions when choosing compression socks is selecting the appropriate compression level. Compression is measured in millimetres of mercury (mmHg), and different levels serve distinctly different purposes. This guide will help you understand what these numbers mean and how to choose the right compression for your specific needs.
What Does mmHg Mean?
Millimetres of mercury (mmHg) is a unit of pressure measurement commonly used in medicine. You may recognise it from blood pressure readings. In the context of compression socks, mmHg indicates how much pressure the sock exerts on your leg. The number typically represents the pressure at the ankle, where graduated compression socks provide their strongest squeeze.
When you see a range like "15-20 mmHg," it means the compression at the ankle falls within that range. The variation accounts for differences in manufacturing and how the sock fits different leg shapes. The pressure decreases as it moves up the leg, typically reaching about 70-80% of the ankle pressure at the calf for knee-high socks.
Understanding the Numbers
A compression rating of 20 mmHg means the sock applies pressure equivalent to a column of mercury 20 millimetres high. For reference, normal atmospheric pressure at sea level is about 760 mmHg, so even "firm" compression socks apply relatively gentle pressure compared to the air around us.
Compression Level Categories
Light Compression: 8-15 mmHg
Light compression is the gentlest level available and is suitable for everyday wellness and minor concerns. At this level, the pressure is subtle but still provides noticeable support. Light compression socks are often indistinguishable from regular dress socks or athletic socks in appearance.
Best suited for:
- Everyday comfort and prevention
- Minor leg fatigue after long days
- Light swelling that comes and goes
- Short periods of sitting or standing
- People new to compression who want to ease into it
- General wellness support for healthy individuals
Light compression socks are available without a prescription and are an excellent introduction to compression therapy. Many people wear them daily simply for the comfort and energy boost they provide.
Moderate Compression: 15-20 mmHg
Moderate compression is the most popular level for non-medical use. It provides meaningful therapeutic benefits while remaining comfortable for extended wear. This level is strong enough to make a real difference in circulation and swelling but gentle enough for all-day use by most people.
Best suited for:
- Travel, especially long-haul flights
- Pregnancy-related leg discomfort
- Occupations requiring prolonged standing (nursing, retail, hospitality)
- Desk jobs with extended sitting
- Minor to moderate varicose veins
- Athletic performance and recovery
- Prevention of leg swelling during long journeys
The Goldilocks Zone
For most people without specific medical conditions, 15-20 mmHg represents the "sweet spot" of compression. It's effective enough to provide real benefits while remaining comfortable for all-day wear. If you're unsure where to start, this is often the best choice.
Firm Compression: 20-30 mmHg
Firm compression moves into more therapeutic territory. At this level, the pressure is strong enough to address moderate to significant venous issues and is often recommended by healthcare providers for specific conditions. While available over the counter in many places, consulting with a doctor before using this level is advisable.
Best suited for:
- Moderate to severe varicose veins
- Post-sclerotherapy (spider vein treatment) recovery
- Moderate oedema (swelling) not caused by systemic disease
- DVT prevention in higher-risk individuals
- Post-surgical recovery for leg procedures
- Chronic venous insufficiency management
- Prevention of recurrent leg ulcers
Firm compression socks require more effort to put on and may feel quite tight initially. Most people adapt to the sensation within a few days of regular wear. Proper sizing is especially critical at this level to ensure even pressure distribution.
Medical Grade: 30-40 mmHg
Medical-grade compression delivers strong therapeutic pressure and should only be used under healthcare supervision. This level is typically prescribed for serious venous conditions and post-surgical recovery scenarios. The socks at this compression level may require specialised fitting and donning techniques.
Best suited for:
- Severe chronic venous insufficiency
- Deep vein thrombosis treatment and prevention
- Post-thrombotic syndrome
- Severe oedema management
- Lymphedema (in combination with other therapies)
- Active or healed venous ulcers
- Post-surgical recovery when prescribed
Medical Supervision Required
Compression levels of 30 mmHg and above should only be worn with guidance from a healthcare provider. These levels can interfere with blood flow if used inappropriately or in the presence of certain conditions like peripheral arterial disease.
Extra Firm: 40-50 mmHg and Above
The highest compression levels are reserved for severe medical conditions and are always prescription-only. These compression garments are often custom-made and require professional fitting. They're used for conditions like severe lymphedema and chronic venous hypertension.
Factors Affecting Your Compression Choice
Selecting the right compression level isn't just about matching symptoms to a chart. Several factors influence which level will work best for you:
Your Physical Activity Level
Active individuals may tolerate and benefit from higher compression during exercise. Athletes often wear 15-20 or even 20-30 mmHg during training. However, for recovery or sleeping, lower compression may be more comfortable.
The Duration of Wear
If you'll be wearing compression socks all day, start with a level that feels comfortable for extended periods. It's better to wear moderate compression consistently than to give up on higher compression because it's uncomfortable.
Climate and Temperature
In hot weather, higher compression can feel more restrictive and warm. Consider lighter compression during summer months or look for socks made with breathable, moisture-wicking materials.
Existing Health Conditions
Certain conditions require specific compression levels or may contraindicate compression entirely. Always consult with a healthcare provider if you have diabetes, peripheral arterial disease, congestive heart failure, or skin conditions affecting your legs.
Quick Reference Guide
- 8-15 mmHg: Everyday wellness, minor fatigue, first-time users
- 15-20 mmHg: Travel, pregnancy, work support, athletics, minor varicose veins
- 20-30 mmHg: Moderate venous issues, post-procedure recovery (consult doctor)
- 30-40 mmHg: Serious venous conditions (prescription/supervision required)
- 40+ mmHg: Severe conditions (prescription and fitting required)
Can You Wear Too Much Compression?
Yes, wearing compression that's too strong for your needs can be counterproductive and potentially harmful. Excessive compression can restrict arterial blood flow, cause numbness or tingling, create skin problems, and in rare cases contribute to tissue damage. This is why it's important to start with an appropriate level and only move to higher compression when medically indicated.
Signs that your compression may be too strong include:
- Numbness or tingling in your feet or toes
- Blue or purple discolouration of the toes
- Increased pain rather than relief
- Skin irritation or breakdown
- Difficulty putting on or removing the socks
- Socks that leave deep indentations in your skin
Transitioning Between Compression Levels
If you're moving from one compression level to another, give yourself time to adjust. When increasing compression, you might start by wearing the new socks for just a few hours and gradually extending wear time over a week or two. When decreasing compression (such as after post-surgical recovery), follow your healthcare provider's guidance on the appropriate timeline.
Many people find it helpful to have socks at different compression levels for different activities. For example, you might wear 15-20 mmHg for daily work and 20-30 mmHg during long flights or after particularly demanding days on your feet.