Edit either value. Decimals and scientific notation supported.
1
in
Decimal
Feet + inches
Whole feet; inches from 0 to less than 12. Non-negative values.
esc
Metrem
Kilometrekm
Centimetrecm
Millimetremm
Micrometreµm
Nanometrenm
Inchin
Footft
Yardyd
Milemi
Nautical milenmi
Chainch
Furlongfur
No units found. Try a name or symbol.
Feet + inches
25.4
mm
Decimal
Feet + inches
Whole feet; inches from 0 to less than 12. Non-negative values.
esc
Metrem
Kilometrekm
Centimetrecm
Millimetremm
Micrometreµm
Nanometrenm
Inchin
Footft
Yardyd
Milemi
Nautical milenmi
Chainch
Furlongfur
No units found. Try a name or symbol.
Feet + inches
CONVERSION
1 in ≈ 25.4 mm
6 significant figures
10 significant figures
15 significant figures
Precision changes displayed rounding, not calculation accuracy.
FORMULAmm = in × 25.4
FORMULA & EXAMPLES
How to convert Inches to millimetres
mm = in × 25.4
Multiply the in reading by 25.4.
Worked examples
0.5 in ≈ 12.7 mm
0.5 × 25.4 ≈ 12.7
12 in ≈ 304.8 mm
12 × 25.4 ≈ 304.8
Frequently asked questions
How do decimal inches relate to ruler fractions?
A decimal inch is a fraction of one inch: 0.5 is 1/2 inch and 0.25 is 1/4 inch. This tool keeps decimal results rather than rounding them automatically to ruler marks.
Inches to millimetres table
Fixed reference · Inch to Millimetre
Reference values use this page’s named pair and default context. Calculator precision and font settings do not change this table.
Inch (in)
Millimetre (mm)
0
0
0.1
2.54
0.5
12.7
1
25.4
2
50.8
5
127
10
254
25
635
50
1270
100
2540
1000
25400
Table results use 10 significant figures; decimal formula coefficients use up to 15. Calculations use the unit definitions before rounding. Extra digits do not improve measurement accuracy.