Numbers to remember/conversions/number rules

cm → inches?

Divide by 2.54.

inches → cm?

Multiply by 2.54.

mm → inches?

Divide by 25.4.

inches → mm?

Multiply by 25.4.

metres → feet?

Divide by 0.3048.

feet → metres?

Multiply by 0.3048.

1 inch = ?

25.4 mm = 2.54 cm.

1 foot = ?

12 inches = 304.8 mm = 0.3048 m.

How many mm in 1 cm?

10 mm.

How many cm in 1 m?

100 cm.

How many mm in 1 m?

1,000 mm.

How many inches in 1 foot?

12 inches.

How many feet in 1 yard?

3 feet.

How many inches in 1 yard?

36 inches.

What is 2.54?

1 inch = 2.54 cm.

What is 25.4?

1 inch = 25.4 mm.

What is 0.3048?

1 foot = 0.3048 m.

What is 304.8?

1 foot = 304.8 mm.

What is 0.001?

1 mil = 0.001 inch.

Decimal → fraction?

Write the decimal over 10, 100, or 1,000, then simplify.

Fraction → decimal?

Divide the numerator by the denominator.

Mixed number → improper fraction?

Whole × denominator + numerator; put the result over the denominator.

Improper fraction → mixed number?

Divide numerator by denominator. Quotient = whole number; remainder = numerator.

Add fractions with the same denominator?

Add the numerators and keep the denominator.

Multiply fractions?

Numerator × numerator; denominator × denominator.

Angles inside a triangle add to?

180°.

Right angle?

90°.

Acute angle?

Less than 90°.

Obtuse angle?

More than 90° and less than 180°.

Straight angle?

180°.

Complementary angles?

Add to 90°.

Supplementary angles?

Add to 180°.

Pythagorean theorem?

a² + b² = c².

In a right triangle, which side is c?

The hypotenuse — longest side, opposite the 90° angle.

Rectangle area?

Length × width.

Rectangle perimeter?

2L + 2W.

Square area?

Side × side.

Square perimeter?

4 × side.

Triangle area?

½ × base × height.

Perimeter means?

Distance around the outside.

Area means?

Space inside.

Basic estimating sequence?

Measure → calculate quantity → account for waste → determine total material.

Why add waste when estimating?

To account for cuts, off-cuts, damage, and unusable pieces.

Before estimating material, what should you identify?

Dimensions, material type, quantity, and layout.

Why is accurate measuring important in estimating?

A small measurement error can become a large material error over a whole job.

Higher gauge number = thicker or thinner steel?

Thinner steel.

Lower gauge number = thicker or thinner steel?

Thicker steel.

Thickest gauge in the chart?

10 gauge.

Thinnest gauge in the chart?

25 gauge.

What happens to mil thickness as gauge number increases?

Mil thickness decreases.

1 mil = ?

0.001 inch.

Steel gauge colours in order?

Blue → Red → Orange → Green → Yellow → White → No colour.

Gauge numbers in colour order?

10 → 12 → 14 → 16 → 18 → 20 → 25.

Mil thicknesses in gauge order?

118 → 97 → 68 → 54 → 43 → 33 → 18 mil.

Blue = ?

10 gauge = 118 mil.

Red = ?

12 gauge = 97 mil.

Orange = ?

14 gauge = 68 mil.

Green = ?

16 gauge = 54 mil.

Yellow = ?

18 gauge = 43 mil.

White = ?

20 gauge = 33 mil.

No colour = ?

25 gauge = 18 mil.

If you forget a steel gauge colour/number, what direction should you remember?

Lower gauge = thicker steel; higher gauge = thinner steel; mil thickness goes down as gauge number goes up.