In this track: Digital value and units
Convert ETH to Wei by hand
Move the value into whole Wei without losing any decimal digits.
Changing metres into millimetres multiplies the count of smaller units. ETH to Wei uses the same idea with eighteen decimal places.
1 ETH = 1000000000 Gwei = 1000000000000000000 Wei.
Choose the conversion factor
Multiply the ETH amount by 10¹⁸. For example, 2 ETH is 2,000,000,000,000,000,000 Wei. Always write the unit next to the result so a later reader does not mistake this for a token amount or a gas price.
Work through a fraction
For 0.025 ETH, move the decimal point eighteen places to the right. The result is 25,000,000,000,000,000 Wei. Another route is 25 ÷ 1000 ETH, then apply the conversion factor; both routes produce the same integer.
Know when to stop
One Wei is the smallest whole native unit. A decimal ETH amount with a meaningful digit beyond its eighteenth decimal place cannot be represented exactly as whole Wei. A converter should reject it or explicitly explain its rounding policy.
Verify in both directions
Enter 0.025 in the ETH field of the converter. Then take the displayed Wei and convert it back. A correct round trip returns 0.025 ETH without changing the underlying amount. This calculation does not use a market price.
How many Wei are in 0.025 ETH?
0.025 × 10¹⁸ equals 25 × 10¹⁵ Wei.
Original explanations by EtherTools. Examples are educational and source-linked; this site is independent of the Ethereum Foundation. Our approach.