Yes, both can prime a batch, and both are popular choices specifically for the character they add alongside carbonation — but neither is pure fermentable sugar the way dextrose or sucrose is, and using a straight corn-sugar weight for either will underdose the batch.
Why they're not 1:1 substitutes
This site's priming sugar calculator has three built-in sugar types — corn sugar, table sugar, and DME — each with a published conversion factor relative to corn sugar's fermentable mass. Honey and maple syrup aren't among them, because both are natural products with real batch-to-batch variation in water content and exact sugar composition, unlike a manufactured, standardised product like dextrose or granulated sucrose.
As a working approximation: honey is commonly cited at roughly 80% fermentable sugar by weight (the rest mostly water, with trace minerals and enzymes), meaning you'd need proportionally more honey by weight than a pure-sugar corn-sugar figure to deliver the same fermentable mass — roughly the corn-sugar dose divided by 0.80. Maple syrup runs lower still, commonly cited around 66% sugar by weight (again, mostly water making up the rest) — needing roughly the corn-sugar dose divided by 0.66.
Working an example
For a standard 18.9 L batch at 68°F targeting 2.4 volumes CO2, the corn-sugar dose is 116.7 g. Scaling by the approximate honey and maple syrup sugar-content figures above (not run through the calculator directly, since neither is a built-in sugar type — treat this as an estimate, not a calculator-verified figure the way the built-in sugar types are): honey would need roughly 146 g; maple syrup roughly 177 g. Both are meaningfully more than the corn-sugar figure by weight, purely because both are diluted with water the pure-sugar corn-sugar baseline doesn't carry.
Why this is an estimate, not a precise dose
Real honey and maple syrup vary batch to batch in exact sugar content — different floral sources, harvest conditions and processing all shift the real figure somewhat from the commonly cited averages used above. If precise carbonation matters to you — competition entries, or simply avoiding the guesswork — corn sugar, table sugar or DME (all with tightly controlled, standardised composition) give a far more reliable dose than a natural product with genuine batch variation. If you're using honey or maple syrup specifically for the flavour and aroma they add (a legitimate, common reason to choose them over plain sugar), treat the resulting carbonation level as an estimate and check an early bottle before assuming the whole batch is dosed exactly on target.
The safety consideration doesn't change
Whichever sugar you use, the same roughly 3.5-volume bottle-safety ceiling applies — see what happens if I use too much priming sugar — and the extra uncertainty in a natural sweetener's real sugar content is one more reason to err toward the lower end of your target CO2 range rather than the top when using one.