There are many important formula in IS:456 and yes it is very difficult to remember each and every formula in **IS 456:2000**. As a civil engineer, you must know that useful formula when you work at the site. In this article, I will share some useful formula from IS:456 civil engineer must remember. I also advise you to go through the entire code for once and focus more on these areas.

**Nominal cover to meet durability requirements**

Not less than

**20 mm** for **mild** exposure.

**30 mm** for **moderate** exposure.

**45 mm** for **severe **exposure.

**50 mm** for v**ery severe** exposure.

**75 mm** for** extreme** exposure.

**Reference: Table 16 of IS 456:2000**

Go through **Table 16 A of IS 456:2000 also. (For fire resistance).**

When you start working at the site, the cover that needs to be provided will be the main concern.

**Know some properties of materials as per the code**

The **nominal maximum size of course aggregates** should not be greater than **1/4th of the thickness of the member**. (Refer to the **clause 5.3.3 of IS 456:2000** for more details.)

**Modulus of elasticity of steel **Es can be taken as **200 Kn/m2**. (Refer to the **clause 5.6.3 of IS 456:2000** for more details).

**Modulus of elasticity of concrete** Ec = **5000 √fck**

where fck is Characteristic compressive strength of concrete in 28 days.

(Refer to the **clause 6.2.1 of IS 456:2000** for more details.)

Unless more accurate calculations are warranted, the **unit weights of plain concrete and reinforced concrete** made with sand and gravel or crushed natural stone aggregate may be taken as **24 kN/m3 and 25 kN/m3 respectively**. (Refer to **clause 19.2 of IS 456:2000** for more details.)

Span to Depth ratio of beams are very important. (Refer to the **clause 23.2.1 of IS 456:2000** for more details.)

Basics of **working stress design** and **Limit stress** **design** are also very important. Just go through those clauses once in a while. You’ll at least know where to find the information required.

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