DDW-2024-010711

pg 1 revised 7/10/2017 – DDW D’yani

CONVERSIONS & FORMULAS
1. Area Formulas
a. 1 square ft. = 144 square inches
b. 1 square yd. = 9 square ft.
c. 1 cubic yd. = 27 cubic ft.
Square or Rectangle Area =
d. Length x Width = ft2 (square feet)
e. Length x width x height = ft3 (cubic feet)

f. Cubic Area = .785 x Diameter2 or
3.14 X Radius2 ( pi x R2) ( pi = 3.14)

2. Horsepower (hp) Formulas
a. horsepower = 550 foot-pounds/second
= 33,000 foot-pounds/minute = 1,980,000 foot-pounds/hour
b. Brake Horsepower = Water Horsepower
Pump Efficiency
c. Efficiency:
% Efficiency = out power
input power

d. Kilowatts (kW) = 0.746 x Motor Horsepower
e. Motor Horsepower = Brake Horsepower
Motor Efficiency
f. Water Horsepower = Q (flow gal/min.) x H (Head in ft.)
3960
g. Wire to Water Efficiency:
Overall Efficiency = Water Horsepower x 100
Electrical Horsepower
3. Treatment Formulas
a. Filtration Rate (gpm/ft2) = Flow (gal/min)
Surface Area (ft2)

b. Percent Strength by Weight = Weight of Solute x 100
Weight of Solution

c. Specific Capacity = Flow (gallons per minute)
Well Drawdown (feet)
d. Surface Loading, GPD/sq. ft. = Flow (gal/day)
Surface Area (sq ft) e. Surface Overflow Rate = gal/day
ft2

4. Other Formulas
Chemical Dosage:
These formulas require to be divided by % of strength.
Flow—Chemical by weight:
a. lbs/day = MGD x mg/L x 8.34
b. lbs/day = gal/min x mg/L x .012

Circumference:
c. 3.14 X Diameter (Pi x Diameter)

Concentration:
d. 1 part per million (ppm) = 1 milligram per liter
=0.0584 grains per gallon =8.34 Pounds per MG 1 pound of weight per million pounds
1 part per billion = 1 ug/L (microgram/Liter)
1 part per million = 1 mg/L (milligram/Liter)

e. CT = Chlorine Concentration (mg/L) x Time (min)

f. Detention time = Tank Volume (gallons)
Flow (gpm or gpd or gph)
Flows:
g. 1 gallons per minute = 1,440 gallons/day
h. 1 cubic foot per second (cfs) = 646,272 gallons/day
= 448.8 gallons per minute
i. 1 million gallons per day = 1.55 cubic ft/sec.=
694.4 gallons per minute
j. Flow Rate =
Q (flow ft3/sec.) = V (velocity ft/sec.) x A (area ft2)

k. Force = Pressure (psi) x Area (inches2)

l. Hydraulics:
2.31 Head Feet = 1 PSI
0.433 PSI = 1.0 Feet of Head
m. Per Capita Water Use =
Water used (gal/day)/total number of people

n. Percent = Part x 100
Whole

o. Specific Gravity =
Solution weight (lbs/gal)
Weight of Water (8.34 lbs/gal)

pg 2 revised 7/10/2017 – DDW D’yani

5. Common Conversions
Volume and Capacity:
a. 1 cubic ft. = 7.48 gallons
b. 1 cubic yd. = 27 cubic ft.
c. 1 quart = 2 pints = 32 fluid ounces
d. 1 liter = 1000 milliliters = 1.06 quarts =
1000 cubic centimeters
e. 1 gallon (gal) = 8 pints = 231 cubic inches =
f. 3.785 liters = 3,785 milliliters
g. 1 acre foot (ac. ft.) = 43,560 cubic feet =
325,851 gallons Time:
h. 1 minute = 60 seconds
i. 1 hour = 60 minutes = 3600 seconds
j. 1 day = 24 hours = 1,440 minutes = 86,400 seconds
k. 1 week = 7 days
l. 1 yr. = 12 months = 52 weeks = 365 days
Lengths:
m. 1 foot = 12 inches
n. 1 yd. = 3 ft. = 36 inches
o. 1 mile = 5,280 ft.

Temperature:
p. Degree Fahrenheit = Degree C x 9/5 +32
q. Degree Centigrade = (Degree F –32) x 5/9

Weight:
r. 1 pound = 16 ounces = 7000 grains =
453.6 grams = .454 kilograms
s. 1 kilogram = 1,000 gm = 2.205 pounds
t. 1 ton = 2,000 pounds
u. 1 gallon of water = 8.34 pounds
v. 1 cubic ft. of water = 62.4 pounds
w. 1 liter of water = 1 kilogram = 1000 grams
x. 1 milliliter of water = 1 gram
y. Density of water = 1gm/ml or 1gm/cc
z. Specific gravity of water = 1.00
aa. Weight of Solution = Weight of Solute + Weight of
Solvent
PIE WHEELS
• To find the quantity above the
horizontal line: multiply the pie
wedges below the line together.
• To solve for one of the pie
wedges below the horizontal line:
cover that pie wedge, then divide
the remaining pie wedge(s) into the
quantity above the horizontal line.