Individual Strings and mixed sets:

Mixed Set: (on a 5 string Pollman bass, 41-3/4 string length):

Kolstein B 67.9#
Spirocore E 61.3#
Kolstein A 63.9#
Kolstein D 67.8#
Spirocore G 47#
from Dr. Gerald N. Johnson, P.E.

D'Addario Orchestra Medium measured on Engelhardts vs. published specs. (The S-9 has a 42" string length, the M-1 41-5/8")

       S-9      M-1     D'Adarrio specification
G    64.3#    63.7#    62#
D    54.6#    63.7#    65.9#
A    58.2#    63.7#    69#
E    59.3#    63.7#    70#
from Dr. Gerald N. Johnson, P.E.

Picato Innovation braided-core D    58#
Jargar Dolce D                      62#

The 2xbass list Wizard of Water, Dr. Gerald N. Johnson, P.E., provides the following instructions to those without scientific measuring devices:

Diameter is only a good measure if the string internal construction is consistent from string to string and there are no voids, its all solid steel. Unfortunately that's not the case so I can't tell much by string diameter. But fortunately most of us do have the resources to measure string tension. This is a way to do it.

The tools needed are a length measure long enough for the mensur and reasonably will calibrated in the half inch or 12 mm range. An empty plastic milk, soda, or juice jug, 1 or two quart or liter is fine. Some paper clips or string, and a supply of clean water and a kitchen measuring cup. Water conveniently weighs very close to 1 gram per milliliter and makes a handy adjustable weight. I'll either neglect the weight of the jug or weigh an empty one here very carefully.

The same measurements can be made with a small spring scale to measure the pressure required for the same half inch deflection, just that water and jug is more commonly available.

Lay the bass on the side with the strings horizontal. It would be a good idea to have a helper make sure the bass doesn't roll over to the belly or off the table.

With a yardstick or steel tape measure the mensur, nut to bridge. That's 59.5a variable and critical to the computation.

Hang an empty 1 quart or 1 liter plastic milk or juice jug on the center of the bass string by a chain of partially straightened paper clips or a loop of string.

With some reasonably precise measuring instrument measure the space between the string under test and a neighbor, dial caliper would be superb, a metal machinist's scale would be really good, a school ruler probably adequate, and a yardstick poor but not to be totally rejected. I can only use thumb width for deflection if the mensur is also in thumb widths...

Add water to the jug until the string spacing changes by 1/2 inch, as closely as possible. That's 12.7 cm. Or something in that range.

Then according to Marks Mechanical engineers handbook figuring deflection of a cable way under load, the universal formula neglecting the weight of the string is:

P = 4 * h * H / L

where h is the deflection, H is the tension, P is the deflecting load, and L is the length between supports. Deflection and length have to be the same units, tension and load also have to be the same units. E.g. mm and Kg or inches and pounds, or mm and pounds...

So for a mensur of 105 mm (41.228"), and a deflection of 0.500 inch, I get this table:

Tension weight ml water us fluid ounces of water
42# 2.032# 924 ml 31.2 fl oz
52# 2.516# 1144 ml 38.6 fl oz
66# 3.194# 1452 ml 49.0 fl oz
75# 3.628# 1650 ml 55.8 fl oz.

Rearranging the formula gives
h = P * L / (4 * H)
and using a 2 pound weight (909 grams)

Tension deflection
42# .492" = 12.5 mm
52# .397" = 10.09 mm
66# .313" = 7.95 mm
75# .276" = 7 mm.

using a 1 kg weight (2.2 pounds)

Tension deflection
42# 13.75 mm = .541"
52# 11.1 mm = .437"
66# 8.75 mm = .344"
75# 7.7 mm = .303"
42# tension is 19.05 Kg-force = 186.825 Newtons.
52# is 23.59 Kg-force = 231.3 Newtons
66# is 29.93 Kg-force = 293.6 Newtons
75# is 34.02 Kg-force = 333.6 Newtons.