Converting from binary to denary

Understanding denary

People use the (or decimal) number system in their day-to-day lives. This system has 10 digits that we can use: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

The value of each is calculated by multiplying by 10 (ie by the power of 10). The first few place values look like this:

ThousandsHundredsTensUnits
(1000s)(100s)(10s)(1s)
Thousands(1000s)
Hundreds(100s)
Tens(10s)
Units(1s)

Working out the value of 1024

Thousands (1000s)Hundreds (100s)Tens (10s)Units (1s)
1024
1 × 1000 +0 × 100 +2 × 10 +4 × 1
Thousands (1000s)1
Hundreds (100s)0
Tens (10s)2
Units (1s)4
Thousands (1000s)1 × 1000 +
Hundreds (100s)0 × 100 +
Tens (10s)2 × 10 +
Units (1s)4 × 1

Converting from binary to denary

To convert a number to denary, start by writing out the binary place values. In denary, the place values are 1, 10, 100, 1000, etc – each place value is 10 times bigger than the last. In binary, each place value is 2 times bigger than the last (ie increased by the power of 2). The first few binary place values look like this:

1286432168421
128
64
32
16
8
4
2
1

Working out the value of 1010 1000:

1286432168421
10101000
1×128 +0×64 +1×32 +0×16 +1×8 +0×4 +0×2 +0×1
128 +0 +32 + 0 +8 +0 +0 +0
1281
640
321
160
81
40
20
10
1281×128 +
640×64 +
321×32 +
160×16 +
81×8 +
40×4 +
20×2 +
10×1
128128 +
640 +
3232 +
160 +
88 +
40 +
20 +
10

So 1010 1000 in binary is equal to 168 in denary.

Machine converting binary number 10101000 into denary number 168

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