Hemoglobin Calculator — Hgb Levels

Use the Hemoglobin Calculator

Convert units, view WHO anemia thresholds, and see an estimated hematocrit from your Hgb value.

How to Use Hemoglobin Calculator — Hgb Levels

1. Step 1: Select Population

   Choose adult male, adult female, pregnancy, or a pediatric group so thresholds match your context.

2. Step 2: Enter Hemoglobin

   Type your hemoglobin in g/dL (most labs) or switch to g/L and enter that value.

3. Step 3: Calculate

   Tap Calculate to view classification, conversions, and the hematocrit estimate.

4. Step 4: Compare Thresholds

   Scroll the WHO bands for mild, moderate, or severe anemia mapped to your group.

5. Step 5: Review Notes

   Hydration, altitude, and smoking can shift results; use your printed lab range as the source of truth.

Key Features

• Instant Hgb classification by age/sex
• g/dL ↔ g/L ↔ mmol/L conversions
• WHO anemia thresholds with severity
• Pregnancy and pediatric ranges
• Estimated hematocrit (Hct) %

Understanding Results

Formula & Conversions

Most labs report hemoglobin in grams per deciliter (g/dL). Our hemoglobin calculator converts to grams per liter (g/L) by multiplying by 10 and approximates millimoles per liter (mmol/L) by dividing g/L by 64.5 (hemoglobin’s molar mass ≈ 64.5 kDa). It also shows a rule‑of‑thumb hematocrit estimate using Hct (%) ≈ 3 × Hgb.

Reference Ranges & Interpretation

Lower cut‑offs commonly used for anemia are about 13.0 g/dL for adult men, 12.0 g/dL for adult non‑pregnant women, and 11.0 g/dL in pregnancy. Pediatric thresholds change with age (for example 11.0 g/dL for 6–59 months, 11.5 g/dL for 5–11 years, 12.0 g/dL for 12–14 years). When below the cut‑off, anemia is often described as mild, moderate, or severe based on bands that differ slightly across groups.

Assumptions & Limitations

Hydration, altitude, smoking, pregnancy, and lab methods can shift hemoglobin without reflecting a disease process. Always compare with your printed lab reference interval and speak with a clinician for diagnosis. The tool is informational and does not replace medical advice.

Complete Guide: Hemoglobin Calculator — Hgb Levels

Interpret values within a CBC using our hemoglobin calculator. View ranges, anemia patterns, and units (g/dL) to support clinical review and conversation.

This hemoglobin calculator converts between common units, classifies results by age and sex (including pregnancy), and shows a rule‑of‑thumb hematocrit estimate. It is designed for quick interpretation alongside your official lab report.

What is hemoglobin?

Hemoglobin (Hgb) is the oxygen‑carrying protein inside red blood cells. Each molecule binds oxygen in the lungs and releases it to tissues throughout the body. Because red blood cells circulate for about 120 days on average, your hemoglobin level reflects both current status and the recent past. Most labs report hemoglobin in grams per deciliter (g/dL), though some use grams per liter (g/L) or, less commonly, millimoles per liter (mmol/L).

A single number rarely tells the full story. Hydration status, altitude, smoking, pregnancy, and medical conditions can shift hemoglobin up or down. That is why your result is usually interpreted along with other parts of the complete blood count (CBC), such as hematocrit (Hct), mean corpuscular volume (MCV), and red cell distribution width (RDW). For a quick complementary view of red cell concentration, try our hematocrit calculator.

How the hemoglobin calculator works

The tool accepts your hemoglobin value in g/dL or g/L and classifies it using widely cited World Health Organization (WHO) cut‑offs for anemia. Because normal ranges differ by age and sex—and pregnancy lowers the expected threshold—the calculator lets you select a population group (adult male, adult female, pregnant, and several pediatric ranges). It then converts to other units, estimates hematocrit using the common rule of thumb Hct ≈ 3 × Hgb, and displays a severity band when your value is below the threshold.

Results here are for education, planning, and conversation. They do not diagnose any condition. Use the number alongside your official report, symptoms, and clinician guidance. If your value is far outside typical ranges or you feel unwell, seek medical care promptly.

Formulas and units

Laboratories most often report hemoglobin in g/dL. To convert to g/L, multiply by 10. To approximate mmol/L, divide g/L by 64.5 (hemoglobin’s molar mass ≈ 64.5 kDa). For example, Hgb 14.0 g/dL equals 140 g/L and roughly 2.17 mmol/L.

• g/L = g/dL × 10
• mmol/L ≈ (g/dL × 10) ÷ 64.5
• Estimated hematocrit: Hct (%) ≈ 3 × Hgb (±3)

If you are reviewing diabetes metrics, remember that some conditions that change red cell lifespan (for example certain anemias, pregnancy, kidney disease, or hemoglobin variants) can shift A1C. If that context is relevant, compare your CBC with our A1C calculator and day‑to‑day readings from the blood sugar calculator.

Reference ranges and interpretation

The calculator displays WHO‑style anemia thresholds: for adult men the lower cut‑off is roughly 13.0 g/dL, for adult non‑pregnant women 12.0 g/dL, and for pregnancy 11.0 g/dL. Pediatric thresholds depend on age: 11.0 g/dL for 6–59 months, 11.5 g/dL for 5–11 years, and 12.0 g/dL for 12–14 years. When your value falls below the cut‑off, severity is often described as mild, moderate, or severe based on bands that differ slightly across groups (for example severe anemia generally means Hgb < 7–8 g/dL, depending on age and pregnancy status).

Upper reference limits are less standardized and vary by lab, geography, altitude, and smokers vs non‑smokers. As a rough guide, Hgb above about 17.5 g/dL in adult men or 15.5 g/dL in adult women is often flagged as elevated. It does not always signal disease; dehydration, living at high altitude, or temporary physiologic shifts can be enough. Use your lab’s printed reference interval as the source of truth and follow up if you are unsure. For a different view on oxygen delivery, you can also check your saturation with the oxygen saturation calculator.

Making sense of your hemoglobin result

Start by confirming the unit (g/dL vs g/L) and the reference interval printed on your report. Then place your value in context: recent illness, hydration, altitude, smoking status, pregnancy, and medications all move hemoglobin. If your number sits near a threshold, re‑check on a day you feel well and well‑hydrated.

Use this hemoglobin calculator to translate units and to see where your value sits relative to common cut‑offs, but rely on your clinician for diagnosis. When you bring your report, include symptoms (fatigue, shortness of breath, headaches), timeline, and any relevant history (dietary changes, bleeding, chronic disease). That information makes interpretation faster and safer.

Factors that shift hemoglobin

Several everyday factors move hemoglobin temporarily. Hydration is one: dehydration concentrates red cells, pushing the number higher, while extra fluids can dilute it. High altitude stimulates erythropoietin (EPO) and, over days to weeks, raises hemoglobin to carry more oxygen in thinner air. Smoking and certain lung or heart conditions can have similar effects. On the other hand, pregnancy often lowers hemoglobin modestly because plasma volume expands faster than red cell mass.

Lab methods, timing, and recent illness also matter. If a result seems unexpected, comparing it with hematocrit and indices such as MCV and RDW can reveal patterns. Persistent fatigue, shortness of breath, or rapid heart rate with a low value deserves timely clinical attention. If kidney function is a question, try our kidney function calculator alongside your CBC.

Common causes of low hemoglobin

Low hemoglobin (anemia) has many causes. The most common worldwide is iron deficiency—often from low dietary intake, increased needs (growth, pregnancy), or blood loss (for example heavy menstrual periods or gastrointestinal bleeding). Other causes include chronic disease and inflammation, kidney disease (reduced EPO), vitamin B12 or folate deficiency, inherited conditions (such as thalassemia), bone marrow disorders, and medication effects. Patterns in MCV help: microcytosis suggests iron deficiency or thalassemia; macrocytosis suggests B12/folate deficiency or certain medications.

If iron deficiency is suspected, clinicians typically check ferritin and iron studies, look for bleeding sources, and address diet. For people tracking cycle‑related blood loss, our menstrual cycle calculator can help plan around heavy days, though it does not diagnose any condition. Staying well hydrated and balancing activity and rest can lessen symptoms while the cause is being addressed.

Common causes of high hemoglobin

Elevated hemoglobin can reflect dehydration, living at altitude, smoking, sleep apnea, chronic lung or heart disease, testosterone or EPO use, or less commonly a bone marrow condition such as polycythemia vera. Context matters: symptoms (headaches, flushing, itching), oxygen saturation, and trends over time guide next steps. Hydration is an easy first check; if your number remains high when well hydrated, bring the report to a clinician for interpretation.

Because oxygen delivery depends on both hemoglobin and saturation, people often look at Hgb together with pulse oximetry. If you are exploring that relationship, the oxygen saturation calculator provides additional context. Fitness or weight goals can also change how you feel at a given Hgb level; if relevant, see the adult BMI calculator for body size context.

Pregnancy and children

Pregnancy expands plasma volume and can lower measured Hgb by dilution. That is expected and reflected in the calculator’s lower pregnancy threshold. Iron needs also rise, so clinicians often recommend prenatal vitamins with iron unless there is a reason not to. For children, cut‑offs change with age because normal red cell production evolves rapidly during growth. If a child’s result is below the expected range, clinicians typically review diet, growth, and family history and may choose a brief iron trial or testing based on the whole picture.

If you are monitoring energy, recovery, or exercise tolerance during pregnancy or adolescence, you might find it useful to look at broader patterns—sleep and hydration especially. Our hydration calculator can help plan daily fluids while you track symptoms and lab trends over time.

Using your results wisely

Use the hemoglobin calculator as a quick lens on your number, not a diagnosis. Confirm units and reference ranges on your printed report; they are the authoritative source. Combine your result with symptoms and history. If your value is unexpectedly low or high, or if you feel unwell, bring the report to a licensed clinician. Extreme values, rapid changes, or symptoms such as chest pain, shortness of breath, or fainting deserve urgent attention.

For everyday planning, trends matter more than a single reading. Re‑check after hydration, rest, or at a consistent time of day. If you are exploring broader health targets, nearby tools—like the hematocrit calculator, A1C calculator, blood sugar calculator, kidney function calculator, and oxygen saturation calculator—offer complementary context.

If your result is unexpected, confirm the unit on your report (g/dL vs g/L), compare with your lab’s reference interval, and repeat the test when you are well‑hydrated and well‑rested. Consistent technique makes changes meaningful—and the hemoglobin calculator keeps unit conversions out of your way.

Frequently Asked Questions