# How to round a number off to 1 significant figure (1sf or 1 sig fig)

## How To Round To 1 Significant Figure Video

Rounding to 1 significant figure is very useful when you
need to estimate. Your 1^{st} significant figure is the first number
from the start of the number you need to round (ignoring any zeros at the
start). Let’s take a look at a few examples:

**Example 1**:

Round 574.89 to 1 significant figure

First highlight your first significant figure:

__5__74.89

Now since the number after 5 is 7 (which is 5 or above) you round the number up to 600.

**Example 2**:

Round 4193 to 1 significant figure.

Again, highlight your first significant figure.

__4__193

Now since the number after 4 is 1 (which is less than 5) you round the number down to 4000.

**Example 3**:

Round 31.586 to 1 significant figure.

Again, highlight your first significant figure.

__3__1.586

Now since the number after 3 is 1 (which is less than 5) you round the number down to 30.

**Example 4:**

Round 6.497 to 1 significant figure.

Again, highlight your first significant figure.

__6__.497

Now since the number after 6 is 4 (which is less than 5) you round the number down to 6.

**Example 5:**

Round 394178.314 to 1 significant figure.

Again, highlight your first significant figure.

__3__94178.314

Now since the number after 3 is 9 (which is 5 or above) you round the number up to 400000.

**Example 6:**

Round 0.003814 to 1 significant figure.

Again, highlight your first significant figure. Since the number is a small number, you ignore the zeros at the start of the number.

0.00__3__814

Now since the number after 3 is 8 (which is 5 or above) you round the number up to 0.004 (don’t put 0’s after 0.003)

**Example 7:**

Estimate this calculation by rounding the numbers off to 1 significant figure.

482 × 12.781

Again all you need to do is round the number off to 1 significant figure.

__4__82
= 500

__1__2.781
= 10

So 500 × 10 is about 5000.

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