The Dirt on Math: Calculators and Conversions for GardenersBy Tamara Galbraith (TexasTam)
October 29, 2010
Before you schedule that delivery of a dump truck full of compost, figure out just what a "cubic yard" really is, because that's what most material companies use in measuring dry materials.
Volume Conversion: Online calculator
Cubic Feet and Yards:
27 Cubic feet = 1 Cubic yard = 1 Ton Avg. Dry Weight
Sq. ft. x deep divided by 324 = Cubic yards.
100 x 2" divided by 324 = .62 Cubic yards
400 x 3" divided by 324 = 3.70 Cubic yards
Even though the bottle gives the recipe for it, do you really need to mix up a gallon of Bt spray? Probably not. When diluting fertilizers and pesticides from concentrate, it's very important to measure accurately. When in doubt, use less than what is recommended by the manufacturer...never more.
One gallon = 4 Quarts/8 pints One cup = 1/2 pint/8 ounces/16 tablespoons
One gallon = 16 cups/128 ounces 1/2 Cup = 4 ounces/8 tablespoons/24 teaspoons
One gallon = 256 tablespoons/768 teaspoons 1/4 Cup = 2 ounces/4 tablespoons/12 teaspoons
One quart = 2 pints/4 cups/32 ounces/64 Tbls. 1 Tablespoon = 1/2 ounce/3 teaspoons
One pint = 2 cups/16 ounces/32 tablespoons
Area Conversion: Online calculator
Length/Distance: Online calculator
Weight and Mass: Online calculator
Online Calculators for Dry Materials
Fabulous calculators that take the guesswork out of some larger garden projects.
Mulch: How much mulch do you need for a certain-sized garden bed? Choose thickness and garden square footage.
Limestone: How much limestone do you need for a certain-sized garden bed? Requires that you know your soil's pH. Enter the pH, soil type and garden size. Limestone adds alkalinity to acidic soil, thus raising the pH.
Sulfur: How much sulfur do you need for a certain-sized garden bed? This calculator requires that you know your soil's pH. Enter the pH, soil type and garden size. Sulfur adds acidity to alkaline soil, thus lowering the pH.
Fertilizer: How much fertilizer should I spread on my lawn? Choose from several different types of fertilizers (blood meal, cow manure, 9-3-6, etc.) and grasses (Bermuda, bluegrass, fescue, etc.)
Calibrating your Fertilizer Spreader: Not an online calculator, but some good tips for figuring out the distribution rate of your rotary or drop spreader.
Actual Nitrogen in a bag of fertilizer. Choose the percentage of nitrogen shown on the bag and the weight of the bag.
Online Calculators for Plants, Grass, Seed
Plants (including perennials, annuals and groundcover), Grass Plugs, Shrubs and Trees: Very general - take with a grain of salt.
Sod Calculator: Calculates rectangular, circular and triangular areas.
Tree Height Calculator: How high is that tree?
Online Calculators for Water Features/Irrigation
Pond calculators based on pond shape (only works with Internet Explorer browsers): Calculates gallons of water, recommended filter, pump and liner sizes
Landscape Irrigation formulas, conversions and calculators: Includes calculators for area and distance, water pressure, flow and water volume, pump efficiency and more.
Miscellaneous Online Calculators
Compost Mix Calculator: Helps design a compost recipe for many common household organic wastes. It will determine the Total C:N Ratio for a mix of materials.
Illuminance (light): Especially handy for orchid growers, who often need to provide the correct "foot candle" measure of luminance.
Smart Phone Apps - Converters, etc.
Converter (Unit Converter): $0.99
BlueSlate Unit Converter (Standard): Free
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