The gas bill is the limit times the price

The formula on the gas pricing page is short enough to memorize. Price per gas is the minimum of the base fee plus your priority fee, and the max fee you set. Gas paid is the gas limit times that price. The base fee has a floor of 100 MON-gwei, which is 100 times 10 to the minus 9 MON, and it moves from block to block with a controller in the EIP-1559 family: slower to rise, faster to fall, aimed at a target the docs put at 160 million gas, 80 percent of a 150 million gas block. Every transaction in one block shares one base fee. The priority fee is how you outbid the person next to you. It is not how you buy a larger safety margin. The safety margin, on this chain, is billed.

A transfer, a token, a swap

The same page gives three anchors, as illustrations, not as a quote you can paste into a router. A native MON transfer is 21,000 gas. An ERC-20 transfer is on the order of 65,000. A typical DEX swap is on the order of 200,000. At the minimum base fee, 200,000 gas is 0.02 MON. A plain transfer is 0.0021 MON. Those numbers are the floor, before a priority fee, and before your wallet multiplies them by a limit it invented. If the base fee is higher when you arrive, multiply again. Do not multiply by a blog’s dollar figure. The docs’ dollar aside, about five hundredths of a cent for a transfer at that floor, goes stale the hour the MON price moves. The MON figure does not.

There is a ceiling as well as a floor. A single transaction may not ask for more than 30 million gas. A block holds 150 million. A wallet that requests 40 million will not be “extra safe”. It will be invalid. A block full of loosely limited transactions can be full of reservations while the receipts look half empty. That is the same fact as the architecture piece, stated as a constraint you can hit with a bad integer.

Pad the estimate by a margin you can say out loud. A limit you cannot justify is a fee you already agreed to pay.

What to do before the sheet

Simulate. Read the estimate. Set the limit near it. If you double it, say why: the call branches, the router sometimes unwraps, the token is weird. If the wallet has already filled a limit five or ten times the estimate, replace it. After the trade, open the receipt and divide the limit by the gas used. A ratio near one means the margin was honest. A ratio of ten means the margin was the trade. MONAF’s own tape, on the research page, is a record of routes that died on exactly this comparison. The useful habit is the division, not the particular pair that failed.

What this piece will not give you

It will not give you a universal limit for “a swap”. Routers change. Hooks change. A limit copied from here will be wrong, and on this chain wrong is expensive rather than merely unused. It will also not tell you the base fee in the next block. That number is on the block. Read it there.