A “good” pH level depends entirely on what you’re measuring. Your blood sits in a narrow window around 7.35 to 7.45, your stomach acid drops as low as 1.0, and your skin hovers near 5.5. Each part of your body, and each substance you interact with, has its own ideal range. Here’s what “good” looks like across the contexts most people care about.
How the pH Scale Works
The pH scale runs from 0 to 14. A pH of 7 is neutral, meaning it’s neither acidic nor alkaline. Anything below 7 is acidic, and anything above 7 is alkaline (also called basic). The scale is logarithmic, so each whole number represents a tenfold difference. A pH of 5 is ten times more acidic than a pH of 6, and a hundred times more acidic than a pH of 7.
Blood pH: The Tightest Range in Your Body
Healthy arterial blood stays between 7.35 and 7.45, just slightly alkaline. Your body defends this range aggressively through your lungs, kidneys, and chemical buffers in your blood. Even small shifts outside this window can disrupt the way your cells function.
When blood drops below 7.35, the condition is called acidosis. When it rises above 7.45, it’s called alkalosis. Both can result from kidney disease, lung problems, uncontrolled diabetes, severe dehydration, or prolonged vomiting. Your body is remarkably good at keeping blood pH stable on its own, which is why most “alkaline diet” claims about changing your blood pH are misleading. Your diet can shift your urine pH, but your blood pH barely budges.
Stomach pH: Extremely Acidic by Design
Your stomach is the most acidic environment in your body, and that’s exactly how it should be. In a fasting state, gastric fluid typically ranges from pH 1.0 to 2.5. After a meal, the pH can climb to 3 through 7 depending on how much food you ate and what it contained.
This acidity serves two purposes: it activates the enzymes that break down protein, and it kills most bacteria and pathogens that enter with your food. When the stomach pH rises too high (becomes less acidic), those enzymes don’t work as efficiently, and digestion slows down.
Skin pH: Mildly Acidic for Protection
Healthy adult skin has a pH of about 5.5. This mild acidity forms what dermatologists call the acid mantle, a thin protective layer that supports beneficial bacteria and blocks harmful ones. When your skin’s pH shifts too high or too low, the barrier weakens. The normal, helpful bacteria on your skin don’t grow as well, and you become more prone to dryness, irritation, and infection.
This is why heavily alkaline soaps (often pH 9 or 10) can leave skin feeling tight and irritated. Cleansers formulated closer to pH 5 to 6 tend to be gentler because they’re closer to your skin’s natural chemistry.
Vaginal pH: Low Acidity Prevents Infection
A typical vaginal pH falls between 3.8 and 4.5 during reproductive years. This acidic environment keeps protective bacteria strong and prevents harmful germs from growing out of control. When vaginal pH rises above 4.5, the risk of bacterial vaginosis and yeast infections increases. Menstruation, sexual activity, certain hygiene products, and hormonal changes can all push pH higher temporarily.
Mouth and Tooth Enamel
Resting saliva has a pH of roughly 7.0, essentially neutral. This matters because tooth enamel starts to weaken when the pH in your mouth drops below about 5.5. Below pH 4.3 to 4.5, enamel actively dissolves even if fluoride is present. Sugary and acidic foods feed bacteria that produce acid, pulling your mouth’s pH down into that danger zone. Saliva naturally brings pH back up and delivers calcium and phosphate that help rebuild enamel, which is one reason dry mouth is a significant risk factor for cavities.
Urine pH: A Wide and Shifting Range
Normal urine pH ranges from 4.6 to 8.0, making it one of the most variable measurements in your body. Unlike blood, urine pH responds directly to what you eat. A diet heavy in fruits, vegetables, and non-cheese dairy products tends to push urine pH higher (more alkaline). A diet rich in meat, fish, and cheese pulls it lower (more acidic).
Doctors sometimes check urine pH when evaluating kidney stone risk or monitoring certain metabolic conditions. On its own, a single urine pH reading doesn’t tell you much about your overall health, but persistent extremes in either direction can signal problems worth investigating.
Drinking Water pH
The U.S. Environmental Protection Agency recommends a drinking water pH between 6.5 and 8.5. This is a secondary standard, meaning it’s about taste, appearance, and pipe corrosion rather than direct health effects. Water below 6.5 can taste sour and corrode metal plumbing, leaching copper or lead into your supply. Water above 8.5 can taste bitter and leave mineral deposits.
Most municipal tap water falls comfortably within this range. If you’re on well water, testing pH is worthwhile because acidic groundwater is common in certain regions and can damage your plumbing over time.
Swimming Pool pH
Pool water should stay between 7.0 and 7.6. This range keeps chlorine effective at killing bacteria while remaining comfortable for swimmers. When pool pH climbs above 8.0, swimmers are at risk of skin rashes. Below 7.0, the water can sting your eyes. High pH also reduces chlorine’s disinfecting power, meaning the pool looks clean but isn’t doing its job.
Garden Soil pH
Most vegetables grow best in soil with a pH between 6.0 and 7.0, with 6.5 considered ideal. In this range, essential nutrients like nitrogen, phosphorus, and potassium are most available to plant roots. Growth generally isn’t hindered anywhere from pH 5.5 to 7.5, but outside that window you’ll likely need to amend your soil.
Soil that’s too alkaline (above 7.5) can lock up iron and zinc, causing yellowing leaves in crops like beans, tomatoes, and sweet corn. This is especially common in compacted, poorly drained soil with excess lime. Soil that’s too acidic can be corrected with agricultural lime, while overly alkaline soil often benefits from sulfur or organic matter like compost. A simple soil test kit from a garden center will tell you where you stand.
Quick Reference by Context
- Blood: 7.35 to 7.45
- Stomach (fasting): 1.0 to 2.5
- Skin: around 5.5
- Vaginal: 3.8 to 4.5
- Saliva: around 7.0
- Urine: 4.6 to 8.0
- Drinking water: 6.5 to 8.5
- Pool water: 7.0 to 7.6
- Garden soil: 6.0 to 7.0
The key takeaway is that “good” pH isn’t a single number. Your body maintains different pH levels in different places for specific biological reasons, and the ideal range for water, soil, or a swimming pool depends on what you need that environment to do.