To calculate hearing loss from an audiogram, you add together the decibel (dB) thresholds at specific frequencies and divide by the number of frequencies tested. The most common method averages three frequencies: 500, 1000, and 2000 Hz. This gives you a number called the pure tone average (PTA), which summarizes how much hearing loss you have in the range most important for understanding speech.
There are several ways to turn audiogram numbers into a meaningful result, depending on whether you want a simple severity grade, a percentage of hearing loss, or a comparison between ears. Here’s how each calculation works.
Reading the Audiogram First
Before you calculate anything, you need to identify the right numbers on the chart. An audiogram plots frequency (pitch) on the horizontal axis from low to high, and hearing level in decibels on the vertical axis, with louder sounds toward the bottom. Each point on the graph represents the quietest sound you could detect at that pitch.
Circles or triangles mark your right ear’s air conduction results. X marks or squares represent the left ear. You may also see bracket-shaped symbols: “<” or “[” for the right ear’s bone conduction, and “>” or “]” for the left. Air conduction tests sound traveling through your ear canal, eardrum, and inner ear together. Bone conduction bypasses the outer and middle ear entirely. The difference between those two measurements, called the air-bone gap, tells you whether your hearing loss involves the middle ear (conductive), the inner ear (sensorineural), or both (mixed).
For calculation purposes, you’ll almost always use the air conduction thresholds, which are the circle and X symbols.
The Pure Tone Average (PTA)
The PTA is the standard starting point. For each ear separately, find the dB values at 500 Hz, 1000 Hz, and 2000 Hz, then take the average:
PTA = (500 Hz + 1000 Hz + 2000 Hz) ÷ 3
For example, if your right ear shows thresholds of 30 dB at 500 Hz, 40 dB at 1000 Hz, and 50 dB at 2000 Hz, your PTA is (30 + 40 + 50) ÷ 3 = 40 dB. These three frequencies were chosen because they cover the range where most speech sounds fall, so the PTA gives a quick picture of how well you can hear conversation.
One important caveat: this three-frequency average works best when hearing loss is relatively flat across pitches. If your audiogram slopes steeply, meaning much worse hearing at higher frequencies, the PTA can underestimate your real-world difficulty. In that case, audiologists sometimes use Fletcher’s method, which averages only the best two of the three frequencies (500, 1000, and 2000 Hz). This tends to match speech understanding more closely when the audiogram isn’t flat.
What Your PTA Number Means
Once you have a PTA, you can classify the severity of your hearing loss using the World Health Organization’s grading scale:
- 0 to 25 dB: Normal hearing
- 26 to 40 dB: Mild hearing loss
- 41 to 60 dB: Moderate hearing loss
- 61 to 80 dB: Severe hearing loss
- 81 dB or greater: Profound hearing loss
A PTA of 40 dB, from the earlier example, falls right at the boundary between mild and moderate. At this level, you’d likely struggle to follow normal conversation in a noisy room and might miss softer speech sounds even in quiet settings.
Calculating a Percentage of Hearing Loss
If you need hearing loss expressed as a percentage, typically for workers’ compensation, disability claims, or legal purposes, the calculation adds an extra frequency and uses a different formula. This method, based on guidelines from the American Medical Association, works in three steps for each ear.
Step 1: Average Four Frequencies
Add the dB thresholds at 500, 1000, 2000, and 3000 Hz, then divide by four. Note this includes 3000 Hz, which the standard PTA does not.
Step 2: Subtract the “Low Fence”
Subtract 25 dB from your four-frequency average. The 25 dB threshold is called the low fence because hearing loss below that level isn’t considered a functional impairment. If your average is 25 dB or less, your percentage is zero for that ear.
Step 3: Multiply by 1.5
Take the result from Step 2 and multiply it by 1.5. This converts the decibel value into a percentage of hearing loss for that ear (called monaural hearing loss).
The full formula looks like this:
Monaural loss % = ((four-frequency average − 25) × 1.5)
So if your four-frequency average is 45 dB, the calculation is (45 − 25) × 1.5 = 30% hearing loss in that ear. Some jurisdictions also add a small percentage (up to 5%) if you have tinnitus, the perception of ringing or buzzing.
Combining Both Ears
Overall hearing impairment is always calculated using both ears, even if only one ear has hearing loss. The formula weights your better ear more heavily because it contributes more to everyday hearing. The standard weighting is 5 to 1: multiply the better ear’s percentage by five, add the worse ear’s percentage, then divide by six.
Binaural loss % = ((better ear % × 5) + worse ear %) ÷ 6
If your better ear has 10% monaural loss and your worse ear has 30%, the binaural hearing impairment is ((10 × 5) + 30) ÷ 6 = 13.3%. This weighting reflects the reality that your stronger ear does most of the heavy lifting in daily communication.
Identifying the Type of Hearing Loss
The audiogram also tells you what kind of hearing loss you have, which matters for treatment decisions. Compare the air conduction symbols (circles and X marks) to the bone conduction symbols (brackets and angle marks) at each frequency.
If air and bone conduction thresholds are close together and both show hearing loss, the problem is in the inner ear or auditory nerve. This is sensorineural hearing loss. If bone conduction is normal but air conduction shows a loss, the gap between them (the air-bone gap) points to a problem in the outer or middle ear, meaning conductive hearing loss. When both lines are depressed and a gap exists between them, it’s mixed hearing loss involving both areas.
Air-bone gaps can range from small to as large as 60 dB, depending on the cause. Common reasons include fluid behind the eardrum, a perforated eardrum, or problems with the tiny bones that transmit sound through the middle ear. The size and pattern of the gap across frequencies can help narrow down the cause.
Checking Your Audiogram’s Accuracy
Most hearing tests include a speech recognition threshold (SRT), which is the softest level at which you can correctly repeat two-syllable words. In a reliable test, the SRT should be close to your PTA, typically within about 6 to 10 dB. A discrepancy larger than 12 dB suggests something may be off, either with the test conditions or the responses, and the results may need to be repeated.
For people with flat or gently sloping audiograms, the PTA and SRT tend to match closely, with an average difference of about 4 dB. The correlation weakens at higher frequencies like 4000 Hz, which is why the standard PTA focuses on lower frequencies where speech energy is concentrated.
A Worked Example
Suppose your audiogram shows these air conduction thresholds for your left ear: 25 dB at 500 Hz, 35 dB at 1000 Hz, 45 dB at 2000 Hz, and 55 dB at 3000 Hz.
Your three-frequency PTA is (25 + 35 + 45) ÷ 3 = 35 dB. That places you in the mild hearing loss range on the WHO scale.
For a percentage calculation, your four-frequency average is (25 + 35 + 45 + 55) ÷ 4 = 40 dB. Subtract the 25 dB low fence to get 15, then multiply by 1.5. Your monaural hearing loss for that ear is 22.5%. If your right ear tested at 0% loss, your binaural impairment would be ((0 × 5) + 22.5) ÷ 6 = 3.75%.
That low binaural number reflects the heavy weighting toward the better ear. Even a significant loss in one ear produces a modest overall impairment percentage when the other ear is normal.