Blood Sugar Calculator
Analyze your blood glucose readings, convert between units, and understand what your levels mean for your health.
Blood Sugar Reading
Blood Sugar Level
100 mg/dL
Prediabetes
🩸mg/dL
100
🔬mmol/L
5.5
📊Est. A1C
5.1%
⏰Type
Fasting
Interpretation
Your blood sugar indicates prediabetes. Consider lifestyle changes.
Risk Assessment
Low risk
Blood Sugar Reference Ranges
Fasting Blood Sugar
| Range | Status |
|---|---|
| < 70 mg/dL | Low |
| 70-99 mg/dL | Normal |
| 100-125 mg/dL | Prediabetes |
| 126+ mg/dL | Diabetes |
2 Hours Post-Meal
| Range | Status |
|---|---|
| < 70 mg/dL | Low |
| 70-139 mg/dL | Normal |
| 140-199 mg/dL | Prediabetes |
| 200+ mg/dL | Diabetes |
Understanding Blood Sugar (Blood Glucose)
Blood sugar (blood glucose) is the main type of sugar found in your blood. It comes from the food you eat and is your body's primary source of energy. Maintaining healthy blood sugar levels is essential for overall health.
Normal Blood Sugar Levels:
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting | <100 mg/dL | 100-125 mg/dL | ≥126 mg/dL |
| 2hr Post-meal | <140 mg/dL | 140-199 mg/dL | ≥200 mg/dL |
| Random | 70-140 mg/dL | — | ≥200 mg/dL + symptoms |
Why Blood Sugar Matters:
- Brain function depends on glucose as its primary fuel
- Chronically high blood sugar damages blood vessels and nerves
- Low blood sugar (hypoglycemia) can be immediately dangerous
- Stable blood sugar promotes energy, mood, and weight management
Blood Sugar Unit Conversion
Blood sugar is measured in different units around the world:
Blood Glucose Unit Conversion
mmol/L to mg/dL:
mg/dL = mmol/L × 18.0182
mg/dL to mmol/L:
mmol/L = mg/dL ÷ 18.0182
Simplified:
mmol/L × 18 ≈ mg/dL
mg/dL ÷ 18 ≈ mmol/L
Where:
- mg/dL= Milligrams per deciliter (US, Japan)
- mmol/L= Millimoles per liter (most other countries)
- 18= Molecular weight conversion factor
Quick Conversion Reference
| mg/dL | mmol/L | Interpretation |
|---|---|---|
| 70 | 3.9 | Low end of normal |
| 90 | 5.0 | Optimal fasting |
| 100 | 5.6 | Upper limit normal fasting |
| 126 | 7.0 | Diabetes threshold (fasting) |
| 140 | 7.8 | Post-meal target ceiling |
| 180 | 10.0 | Diabetes target ceiling (post-meal) |
| 200 | 11.1 | Diabetes threshold (random) |
How to Use This Blood Sugar Calculator
Our calculator converts between blood glucose units and interprets your results:
- Enter Blood Sugar Value: Your measured glucose level
- Select Input Unit: mg/dL or mmol/L
- Select Context: Fasting, post-meal, or random
- View Results:
- Converted value in both units
- Interpretation (normal, prediabetes, diabetes range)
- Target ranges for your situation
When to Test Blood Sugar:
- Fasting: Morning before eating (most important for diagnosis)
- Pre-meal: Right before eating
- Post-meal: 1-2 hours after eating (shows glucose response)
- Bedtime: Helps predict overnight levels
- Random: Anytime, especially if symptoms occur
How to Test Blood Sugar Accurately
Proper technique ensures accurate readings:
Preparation:
- Wash hands with soap and warm water (not alcohol wipes)
- Dry hands completely
- For fasting tests: no food or drink (except water) for 8-12 hours
- For post-meal: test exactly 2 hours after first bite
Testing Steps:
- Insert test strip into meter
- Prick the side of a fingertip (less painful than the pad)
- Gently squeeze for a drop of blood
- Touch blood drop to test strip
- Wait for result and record it
Tips for Consistent Results:
- Test at consistent times each day
- Don't squeeze finger too hard (can dilute blood with fluid)
- Use fresh test strips (check expiration)
- Store strips properly (away from heat and humidity)
- Calibrate meter as recommended
Managing Blood Sugar Levels
Strategies for maintaining healthy blood sugar:
Dietary Approaches:
- Choose complex carbohydrates over simple sugars
- Include protein and healthy fats with meals
- Eat fiber-rich foods (slows glucose absorption)
- Control portion sizes, especially of carbohydrates
- Limit sugary drinks and processed foods
Physical Activity:
- Exercise helps cells use glucose more effectively
- Walking after meals can significantly lower post-meal spikes
- Aim for 150+ minutes of moderate activity weekly
- Strength training improves insulin sensitivity
Lifestyle Factors:
- Sleep: Poor sleep increases insulin resistance
- Stress: Cortisol raises blood sugar
- Weight: Even 5-7% weight loss improves blood sugar
Signs of High Blood Sugar (Hyperglycemia):
- Increased thirst and frequent urination
- Fatigue and blurred vision
- Slow-healing wounds
Signs of Low Blood Sugar (Hypoglycemia):
- Shakiness, sweating, anxiety
- Confusion, irritability
- Fast heartbeat
- Treat immediately with fast-acting glucose
Blood Sugar Target Ranges
Target ranges vary based on individual circumstances:
General Targets for Adults with Diabetes:
- Fasting/Pre-meal: 80-130 mg/dL (4.4-7.2 mmol/L)
- 1-2 hours post-meal: <180 mg/dL (<10 mmol/L)
- Bedtime: 100-140 mg/dL (5.6-7.8 mmol/L)
Tighter Targets (if achievable without hypoglycemia):
- Fasting: 70-100 mg/dL
- Post-meal: <140 mg/dL
- Best for younger, healthier individuals
Relaxed Targets:
- For elderly or those with hypoglycemia risk
- Fasting: 100-150 mg/dL
- Post-meal: <200 mg/dL
Continuous Glucose Monitoring (CGM) Targets:
- Time in Range (70-180 mg/dL): >70% of the day
- Time below 70 mg/dL: <4% of the day
- Time below 54 mg/dL: <1% of the day
Always work with your healthcare provider to determine your personal targets.
Worked Examples
Convert mg/dL to mmol/L
Problem:
A US blood sugar reading is 120 mg/dL. Convert to mmol/L for international reference.
Solution Steps:
- 1Original reading: 120 mg/dL
- 2Conversion formula: mmol/L = mg/dL ÷ 18
- 3120 ÷ 18 = 6.67 mmol/L
- 4Interpretation: Slightly elevated for fasting, normal for post-meal
Result:
120 mg/dL = 6.7 mmol/L | Prediabetes range if fasting, normal if post-meal
Convert mmol/L to mg/dL
Problem:
A UK lab result shows fasting glucose of 5.2 mmol/L. Convert to mg/dL.
Solution Steps:
- 1Original reading: 5.2 mmol/L
- 2Conversion formula: mg/dL = mmol/L × 18
- 35.2 × 18 = 93.6 mg/dL
- 4Interpretation: Normal fasting glucose
Result:
5.2 mmol/L = 94 mg/dL | Normal fasting blood sugar
Interpret Post-Meal Reading
Problem:
Blood sugar 2 hours after dinner is 165 mg/dL. Is this concerning?
Solution Steps:
- 1Reading: 165 mg/dL (9.2 mmol/L)
- 2Context: 2 hours post-meal
- 3Non-diabetic target: <140 mg/dL
- 4Diabetic target: <180 mg/dL
- 5This reading is elevated for non-diabetics
- 6Within target for most diabetics but room for improvement
Result:
165 mg/dL post-meal | For non-diabetics: elevated (discuss with doctor) | For diabetics: within standard target
Tips & Best Practices
- ✓Test blood sugar at consistent times each day for meaningful comparisons
- ✓Wash hands with warm water and soap before testing - don't use alcohol wipes
- ✓Keep a blood sugar log to identify patterns and triggers
- ✓Walking for 10-15 minutes after meals can significantly lower post-meal spikes
- ✓Store test strips properly and check expiration dates for accurate readings
- ✓Know your personal target ranges - they may differ from general guidelines
- ✓Recognize symptoms of both high and low blood sugar for safety
- ✓Share your blood sugar records with your healthcare provider at every visit
Frequently Asked Questions
Historical and regional differences led to different measurement conventions. The US, Japan, and some other countries use mg/dL (milligrams per deciliter), while most of Europe, Australia, Canada, and other countries use mmol/L (millimoles per liter). Both measure the same thing - the concentration of glucose in blood - just using different scales. The conversion factor is approximately 18.
It depends on what you're trying to learn. Fasting (morning, 8+ hours without food) gives your baseline and is most important for diagnosis. Post-meal (1-2 hours after eating) shows how your body handles food. Testing before and after meals helps identify problematic foods. Before bed checks help predict overnight levels. For most people, fasting and occasional post-meal tests provide the most useful information.
This is called the 'dawn phenomenon' and is quite common. Your liver releases glucose in the early morning hours to prepare your body for waking, and for some people this raises fasting glucose. Stress hormones in the morning also contribute. This doesn't necessarily mean your diabetes management is poor - discuss with your doctor about adjusting medication timing or evening snacks if it's significantly elevated.
FDA-approved meters are required to be within ±15% of lab values for readings above 100 mg/dL and within ±15 mg/dL for lower readings. This means a 'true' value of 100 mg/dL could read as 85-115 mg/dL on a home meter. Factors affecting accuracy include strip quality, temperature, technique, and meter calibration. For important decisions, lab testing is more accurate.
Yes. Hypoglycemia (low blood sugar, below 70 mg/dL) can be dangerous, especially for diabetics on insulin or certain medications. Symptoms include shakiness, sweating, confusion, and anxiety. Severe hypoglycemia can cause seizures or loss of consciousness. Treat low blood sugar immediately with 15-20 grams of fast-acting carbohydrates (glucose tablets, juice, regular soda), then retest in 15 minutes.
Yes, significantly. Stress hormones (cortisol, adrenaline) signal the liver to release stored glucose, raising blood sugar. This 'fight or flight' response can increase blood sugar even without eating. Physical stress (illness, injury) also raises blood sugar. Managing stress through exercise, sleep, and relaxation techniques can help improve blood sugar control.
Sources & References
Last updated: 2026-01-22