Given a simple address to address mapping as follows:

mapping (address => address) public matches;

Can someone give me an idea of the cost in ether to store something like this in a solidity contract? I understand that there are gas costs associated with every alteration of the blockchain and storage is expensive but I am having trouble finding estimations of what simple storage like a mapping would cost.

The feasibility of my Dapp idea depends on storing mappings from address to address cheaply. Ideally around 1 cent USD or so. If mappings are more expensive are there any workarounds? Thanks.

1 Answer 1


In the simplest implementation I can think of:

pragma solidity ^0.4.6;

contract Mapping {
    mapping(address => address) public matches;

    function writeMapping(address addr) {
        matches[addr] = msg.sender;
  1. First write 42K gas
  2. Overwrite 27K gas

enter image description here

Gas price in Eth and ETH price in $ both float on markets, so any estimate would be a forecast.

The gas cost operations are knowable and should be consistent (in the example) but are subject to periodic change at the protocol level. That is, if the cost/OP table is adjusted in the future.

Hope it helps.

  • Thanks Rob. Any idea where I can find what 42K gas equates to at this moment or perhaps before the price rise? Commented Apr 6, 2017 at 10:55
  • It's a two-step. I see a gas price of 18gwei right here: ethstats.net. Convert to 0.000000018ETH ... so 42K times that. Then off to exchange etc., to convert ETH to USD, etc. Good indication of current cost. Usual disclaimer: Past results are not indicative of future performance ... Commented Apr 6, 2017 at 11:21

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