Update 5/11/2023: DMARC analyzer has shut down their SPF lookup tool. Here’s another that will count the lookups: DMARCly.
dmarc analyzer is, hands down, our favorite SPF checker.
Not only does it validate the domain’s SPF record, it expands out all of the calls, AND tells you the count of the DNS lookups.
One of the little known facts about SPF is that the specification says that there can only be up to 10 DNS lookups. If you go past ten, the entire record could be ignored, and then you’re just as bad off if you didn’t have an SPF record at all and you’re living with a false sense of security.