diff --git a/endaq/calc/utils.py b/endaq/calc/utils.py
index 2ba7eb9..c3b16ce 100644
--- a/endaq/calc/utils.py
+++ b/endaq/calc/utils.py
@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 import typing
-from typing import Optional, Union
+from typing import Optional, Union, Literal
 import warnings
 
 import numpy as np
@@ -161,9 +161,9 @@ def resample(df: pd.DataFrame, sample_rate: Optional[float] = None) -> pd.DataFr
         index=resampled_time.astype(df.index.dtype),
         columns=df.columns,
     )
-    
+
     resampled_df.index.name = df.index.name
-    
+
     return resampled_df
 
 
@@ -343,3 +343,119 @@ def convert_units(
         for i, c in enumerate(df.columns):
             converted_df[c] = vals[:, i]
         return converted_df
+
+
+def to_altitude(df: pd.DataFrame,
+                base_press: Optional[float] = 101325,
+                base_temp: Optional[float] = 15,
+                temp_col_index: Optional[int] = None,
+                press_col_index: Optional[int] = None,
+                units: Literal['m', 'ft'] = 'm') -> pd.DataFrame:
+    """
+    Converts pressure (Pascals) to altitude (feet or meters) up to 50km.
+
+    :param df: pandas DataFrame of one of the temperature/pressure channels. 
+        A pressure column should be present, if not, raise an error
+    :param base_press: P_b; reference pressure (pressure at sea level) in
+        Pascals (Pa). If set to None, use the first pressure measurement
+        included in the dataframe (df)
+    :param base_temp: T_b reference temperature (temperature at sea level) in 
+        Celsius (C). If set to None and a Temperature column exists in the
+        dataframe (df), use the first listed temperature value. If set to None
+        and no temperature column exists, error out
+    :param temp_col_index: the index (starting at 0) in the dataframe (df) of
+        the temperature column to pull data from.
+    :param press_col_index: the index (starting at 0) in the dataframe (df) of
+        the pressure column to pull data from
+    :param units: determines if altitude is represented in meters ('m') or feet 
+        ('ft') in both the input and output dataframes
+    :returns: a pandas DataFrame with the same Index values as the 
+        input, and an added column of “Altitude (m)” or “Altitude (ft)” data
+    """
+    # Column Name Placeholders
+    temp_col = None
+    press_col = None
+
+    # Conversion Constants
+    C_K = 273.15 # Celsius to Kelvin Constant (C + 273.15 = K)
+    ft_m = 0.3048 # Feet to Meters Constant (ft * 0.3048 = m) & (m / 0.3048 = ft)
+
+    # Constants
+    h_b = 0 # Reference Height of Sea Level (m)
+    h_sb = 11000 # Height at the Base of the Stratosphere (meters)
+    h_st = 50000 # Height at the Top of the Stratosphere (meters)
+    L_b = -0.0065 # Standard Temperature Lapse Rate [K/m]
+    g_0 = 9.80665 # Gravitational Acceleration Constant [m/s^2]
+    R = 8.31432 # Universal Gas Constant [N*m/mol*K]
+    M = 0.0289644 # Molar Mass of Earth's Air [kg/mol]
+    top_stratosphere_pressure = 100 # Air Pressure at Stratopause (1mb)=[100 Pa]
+
+    # Finding pressure column
+    if press_col_index is None:
+        for col in df.columns:
+            if "press" in col.lower():
+                press_col = col
+                press_col_index = df.columns.get_loc(press_col)
+                break
+        if press_col is None:
+            raise ValueError("Pressure column not found.")
+    else:
+        press_col = df.columns[press_col_index]
+
+    # Checking for base temp and converting to K
+    if base_temp == None:
+        if temp_col_index is None:
+            for col in df.columns:
+                if "temp" in col.lower():
+                    temp_col = col
+                    temp_col_index = df.columns.get_loc(temp_col)
+                    break
+            if temp_col is None:
+                raise ValueError('Temperature column not found.')
+        T_b = df.iloc[0, temp_col_index] + C_K # Standard Temperature in Kelvin
+        T_bS = T_b -71.5 # Temperature at start of Stratosphere
+    else:
+        T_b = base_temp + C_K # Standard Temperature in Kelvin
+        T_bS = T_b -71.5 # Temperature at start of Stratosphere
+
+    # Checking for base pressure
+    if base_press == None:
+        # Set to first pressure recording in the dataframe
+        P_b = df.iloc[0, press_col_index] # Static Pressure in Pascals
+    else:
+        P_b = base_press # Static Pressure in Pascals
+
+    # Pressure at base of Stratosphere
+    base_stratosphere_pressure = (P_b * (1 + (L_b / T_b) * (h_sb - h_b)) **
+                                    ((-g_0 * M) / (R * L_b)))
+
+    # List of Altitudes to be added to Dataframe
+    altitude_column = []
+
+    # Calculate Altitude for the DataFrame
+    for index, row in df.iterrows():
+        P = row[press_col]
+        if P > base_stratosphere_pressure:
+            h = h_b + (T_b / L_b) * (((P / P_b) ** ((-R * L_b) / (g_0 * M))) - 1)
+            altitude_column.append(h)
+        elif top_stratosphere_pressure < P < base_stratosphere_pressure:
+            h = h_sb + ((R * T_bS * np.log(P / base_stratosphere_pressure)) /
+                        (-g_0 * M))
+            altitude_column.append(h)
+        else:
+            raise ValueError("Altitudes above stratosphere not supported.")
+
+    # Convert Altitude back to feet if specified
+    if units == 'ft':
+        altitude_column = [x / ft_m for x in altitude_column]
+        # Add "Altitude (ft)" Column to Copy of Original Dataframe
+        alt_df = df.copy()
+        alt_df["Altitude (ft)"] = altitude_column
+
+    # Add "Altitude (m)" Column to Copy of Original Dataframe
+    if units == 'm':
+        alt_df = df.copy()
+        alt_df["Altitude (m)"] = altitude_column
+
+    # Return DataFrame with New Altitude Column
+    return alt_df
diff --git a/setup.py b/setup.py
index 48bda63..bdf00d5 100644
--- a/setup.py
+++ b/setup.py
@@ -26,7 +26,7 @@ def get_version(rel_path):
     "ebmlite>=3.2.0",
     "idelib>=3.2.8",
     "jinja2",
-    "numpy>=1.19.5",
+    "numpy>1.19.5",
     "pandas>=1.3",
     "plotly>=5.3.1",
     "pynmeagps",
diff --git a/tests/batch/test_core.py b/tests/batch/test_core.py
index 7a1a136..f7561c3 100644
--- a/tests/batch/test_core.py
+++ b/tests/batch/test_core.py
@@ -292,7 +292,7 @@ def assert_output_is_valid(output: endaq.batch.core.OutputStruct):
 @pytest.mark.filterwarnings("ignore:no acceleration channel in:UserWarning")
 @pytest.mark.filterwarnings(
     "ignore"
-    ":nperseg .* is greater than input length .*, using nperseg .*"
+    ":.*nperseg.* is greater than (signal|input) length.*, using nperseg .*"
     ":UserWarning"
 )
 def test_aggregate_data(getdata_builder):
diff --git a/tests/calc/csv_to_df/beyond_stratosphere.csv b/tests/calc/csv_to_df/beyond_stratosphere.csv
new file mode 100644
index 0000000..53731f0
--- /dev/null
+++ b/tests/calc/csv_to_df/beyond_stratosphere.csv
@@ -0,0 +1,2 @@
+Pressure (Pa),Temperature (C)
+25,15
diff --git a/tests/calc/csv_to_df/default_sea_lvl.csv b/tests/calc/csv_to_df/default_sea_lvl.csv
new file mode 100644
index 0000000..75cb987
--- /dev/null
+++ b/tests/calc/csv_to_df/default_sea_lvl.csv
@@ -0,0 +1,18 @@
+Pressure (Pa),Temperature (C)
+101325,15
+100000,
+95000,
+90000,
+85000,
+80000,
+75000,
+70000,
+65000,
+60000,
+55000,
+50000,
+45000,
+40000,
+35000,
+30000,
+25000,
diff --git a/tests/calc/csv_to_df/keys/base_values_none.csv b/tests/calc/csv_to_df/keys/base_values_none.csv
new file mode 100644
index 0000000..0bc8d1f
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/base_values_none.csv
@@ -0,0 +1,18 @@
+Key,base settings = None
+0.00
+110.88
+540.34
+988.50
+1457.30
+1948.99
+2466.23
+3012.18
+3590.69
+4206.43
+4865.22
+5574.44
+6343.62
+7185.44
+8117.27
+9163.96
+10362.95
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/default_settings.csv b/tests/calc/csv_to_df/keys/default_settings.csv
new file mode 100644
index 0000000..74291a5
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/default_settings.csv
@@ -0,0 +1,18 @@
+Key,settings are default
+0.00
+110.88
+540.34
+988.50
+1457.30
+1948.99
+2466.23
+3012.18
+3590.69
+4206.43
+4865.22
+5574.44
+6343.62
+7185.44
+8117.27
+9163.96
+10362.95
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/diff_base_pressure.csv b/tests/calc/csv_to_df/keys/diff_base_pressure.csv
new file mode 100644
index 0000000..486f9f3
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/diff_base_pressure.csv
@@ -0,0 +1,18 @@
+Key,the base pressure is not set to the default value
+-111.16
+0
+430.53
+879.82
+1349.79
+1842.71
+2361.25
+2908.57
+3488.53
+4105.81
+4766.26
+5477.25
+6248.37
+7092.29
+8026.46,
+9075.77
+10277.77
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/diff_base_temp.csv b/tests/calc/csv_to_df/keys/diff_base_temp.csv
new file mode 100644
index 0000000..7d580ee
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/diff_base_temp.csv
@@ -0,0 +1,18 @@
+Key,the base temperature is not set to the default value
+0.00
+116.66
+568.47
+1039.96
+1533.16
+2050.45
+2594.61
+3168.99
+3777.61
+4425.40
+5118.48
+5864.62
+6673.85
+7559.48
+8539.82
+9641.00
+10902.40
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/diff_temp_and_pressure.csv b/tests/calc/csv_to_df/keys/diff_temp_and_pressure.csv
new file mode 100644
index 0000000..2e72d29
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/diff_temp_and_pressure.csv
@@ -0,0 +1,18 @@
+Key,the base temperature and pressure are not set to default values
+-116.95
+0.00
+452.94
+925.62
+1420.06
+1938.64
+2484.17
+3059.98
+3670.13
+4319.54
+5014.37
+5762.38
+6573.63
+7461.49
+8444.29
+9548.22
+10812.79
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/stratosphere.csv b/tests/calc/csv_to_df/keys/stratosphere.csv
new file mode 100644
index 0000000..41bbcdf
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/stratosphere.csv
@@ -0,0 +1,12 @@
+Key,altitude is in the stratosphere
+11784.05
+12452.21
+13199.14
+14045.95
+15023.51
+16179.72
+17594.82
+19419.19
+21990.49
+26386.17
+35177.52
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/keys/units_feet.csv b/tests/calc/csv_to_df/keys/units_feet.csv
new file mode 100644
index 0000000..a250c2a
--- /dev/null
+++ b/tests/calc/csv_to_df/keys/units_feet.csv
@@ -0,0 +1,18 @@
+Key,units are set to feet ('ft')
+0.00
+363.79
+1772.76
+3243.11
+4781.17
+6394.32
+8091.29
+9882.49
+11780.47
+13800.61
+15962.0
+18288.84
+20812.4,
+23574.27
+26631.46
+30065.48
+33999.16
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/press_error.csv b/tests/calc/csv_to_df/press_error.csv
new file mode 100644
index 0000000..6e4fcb5
--- /dev/null
+++ b/tests/calc/csv_to_df/press_error.csv
@@ -0,0 +1,2 @@
+Temperature (C)
+15
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/stratosphere.csv b/tests/calc/csv_to_df/stratosphere.csv
new file mode 100644
index 0000000..55600fb
--- /dev/null
+++ b/tests/calc/csv_to_df/stratosphere.csv
@@ -0,0 +1,12 @@
+Pressure (Pa),Temperature (C)
+20000,-55
+18000
+16000
+14000
+12000
+10000
+8000
+6000
+4000
+2000
+500
\ No newline at end of file
diff --git a/tests/calc/csv_to_df/temp_error.csv b/tests/calc/csv_to_df/temp_error.csv
new file mode 100644
index 0000000..1e3223a
--- /dev/null
+++ b/tests/calc/csv_to_df/temp_error.csv
@@ -0,0 +1,18 @@
+Pressure (Pa),
+101325,
+100000,
+95000,
+90000,
+85000,
+80000,
+75000,
+70000,
+65000,
+60000,
+55000,
+50000,
+45000,
+40000,
+35000,
+30000,
+25000,
diff --git a/tests/calc/test_utils.py b/tests/calc/test_utils.py
index b012c89..b8a5ea9 100644
--- a/tests/calc/test_utils.py
+++ b/tests/calc/test_utils.py
@@ -5,6 +5,10 @@
 import numpy as np
 import pandas as pd
 
+import sys
+import os
+sys.path.insert(0, os.path.realpath(os.path.join(__file__, '..', '..', '..')))
+
 from endaq.calc import utils
 
 
@@ -107,3 +111,61 @@ def test_convert_units():
     df = pd.DataFrame({'Val': [-40, 0, 10]})
     np.testing.assert_allclose(utils.convert_units('degC', 'degF', df).Val[0], -40)
     np.testing.assert_allclose(utils.convert_units('degC', 'degF', df).Val[1], 32)
+
+
+# Dataframes for the following altitude test
+df_1 = pd.read_csv("tests/calc/csv_to_df/default_sea_lvl.csv")
+df_strat = pd.read_csv("tests/calc/csv_to_df/stratosphere.csv")
+
+@pytest.mark.parametrize("kwargs, key", [
+    ({"df": df_1}, "default_settings.csv"),
+    ({"df": df_1, "base_temp": 30}, "diff_base_temp.csv"),
+    ({"df": df_1, "base_press": 100000}, "diff_base_pressure.csv"),
+    ({"df": df_1, "base_temp": 30, "base_press": 100000}, "diff_temp_and_pressure.csv"),
+    ({"df": df_1, "units":'ft'}, "units_feet.csv"),
+    ({"df": df_1, "base_press": None, "base_temp": None}, "base_values_none.csv"),
+    ({"df": df_strat}, "stratosphere.csv"),
+    ])
+def test_to_altitude(kwargs, key):
+    """
+    Tests the accuracy of the to_altitude function, which converts air pressure
+    to altitude. 
+    """
+    possible_altitude_cols = ['Altitude (m)', 'Altitude (ft)']
+    altitude_col = None
+
+    key_df = pd.read_csv("tests/calc/csv_to_df/keys/" + key)
+    key_list = key_df['Key'].tolist()
+
+    to_alt_df = utils.to_altitude(**kwargs)
+    for col in possible_altitude_cols:
+        if col in to_alt_df.columns:
+            altitude_col = col
+            break
+
+    to_alt_list = to_alt_df[altitude_col].tolist()
+    to_alt_list = [round(num, 2) for num in to_alt_list]
+    assert (to_alt_list == key_list
+            ), f"Equation is not accurate when {key_df.columns[1]}."
+
+
+# Dataframes for the following altitude error test
+df_err_temp = pd.read_csv("tests/calc/csv_to_df/temp_error.csv")
+df_err_press = pd.read_csv("tests/calc/csv_to_df/press_error.csv")
+df_err_strat = pd.read_csv("tests/calc/csv_to_df/beyond_stratosphere.csv")
+
+@pytest.mark.parametrize("kwargs, error_message", [
+    ({"df": df_err_temp, "base_temp": None},
+     "there's no temperature column and base_temp = None"),
+    ({"df": df_err_press, "base_press": None},
+     "there's no pressure column and base_press = None"),
+    ({"df": df_err_strat},
+     "altitude is above the stratosphere (50km)"),
+    ])
+def test_to_altitude_errors(kwargs, error_message):
+    """
+    Tests that the to_altitude function raises errors when expected to.
+    """
+    with pytest.raises(ValueError) as exc_info:
+        utils.to_altitude(**kwargs)
+    assert (exc_info.type == ValueError), f"Error not raised when {error_message}."