How can I send a nat value to a contract that represents a data type which is not a whole number?

For example, the xtzToToken entrypoint of the tzBTC contract allows a user to call the xtzToToken entrypoint and send an argument of nat minTokensBought. If I want to send a value that is between 1 and 0 for this argument, how would I do so>

Here is what I've tried (unsuccessfully) via the tezos=client:

tezos-client --dry-run transfer 10000 from alice to KT1TxqZ8QtKvLu3V3JH7Gx58n7Co8pgtpQU5 \
                --entrypoint xtzToToken \
                --arg '(Pair "tz1eYpX4e1nu7e3cvtF7UvKFqUvWDahte1ot" (Pair 1/2 "2021-09-01T09:57:00Z"))' \
                --burn-cap 999


tezos-client --dry-run transfer 10000 from alice to KT1TxqZ8QtKvLu3V3JH7Gx58n7Co8pgtpQU5 \
                --entrypoint xtzToToken \
                --arg '(Pair "tz1eYpX4e1nu7e3cvtF7UvKFqUvWDahte1ot" (Pair 0.5 "2021-09-01T09:57:00Z"))' \
                --burn-cap 999 

1 Answer 1


Its not possible to send lower than 1 mutez. nat is also required to be a whole number.

Tezos/XTZ has 6 decimal places. When a user sees "1 XTZ" in an app, that is represented as 1000000 on the blockchain (6 zeros for 6 decimal places). The blockchain and RPC deal in this smaller scale (called mutez) and its up to each application to scale it up to XTZ when displaying to a user.

It is the same for all tokens. tzBTC has 8 decimal places, so 1 tzBTC, is made up of 100000000 satoshi's.

When you are doing this:

(Pair 1 "2021-09-01T09:57:00Z")

you are not sending 1 XTZ, you are sending 1 mutez (1/1000000 of an XTZ). Sending 1 XTZ would look like this:

(Pair 1000000 "2021-09-01T09:57:00Z")
  • So if I want to send a .62 value for minTokensBought to the addLiquidity entrypoint, I would send a value of (.62 * 100000000) or 62000000? Also, how can I look at a contracts code on an explorer like tzkt.io to see the amount of decimal places that token uses?
    – Whirlybird
    Jul 30, 2021 at 10:46
  • Also it may be worth calling out that the argument I'm passing isn't a value for tzBTC, it's a value for the LQT token found here: granadanet.tzkt.io/KT1AafHA1C1vk959wvHWBispY9Y2f3fxBUUo/…
    – Whirlybird
    Jul 30, 2021 at 10:50
  • @Whirlybird Fa1.2 tokens have no standard way to record decimal places, typically you check their website. FA2 contracts have a metadata field thats stored offchain and holds this info. The Better Call dev explorer manually indexes token data. If you search for a contract and click on the "Tokens" tab you can see the metadata. Here for example is Ethtz, where you can see that it has 18 decimal places: better-call.dev/mainnet/KT19at7rQUvyjxnZ2fBv7D9zc8rkyG7gAoU8/…
    – Simon McLoughlin
    Jul 30, 2021 at 14:57

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