The Talmud tells us (Makkot 23b) that, at Sinai, G‑d transmitted 613 mitzvot to Moses—248 positive commandments (dos) and 365 negative commandments (don'ts). When counting, however, we find that there are many more than 613 biblical obligations and prohibitions. Thus we need to explain the formula by which we determine whether a particular precept is counted as part of the 613 or not.

Maimonides used 14 principles to make this determination:

Principle 1

Do not count Rabbinic Commandments in this list. E.g., lighting Chanukah candles or reciting the Hallel.

Indeed, this seems obvious, for the Talmud says that 613 mitzvot "were given to Moses at Sinai," and rabbinic mitzvot were not instituted until later dates. But in truth, we follow rabbinic rulings because of a biblical mandate: "You shall not divert from the word they tell you, either right or left" (Deuteronomy 17:11); and as such, before performing a rabbinic mitzvah, we say a blessing in which we thank G‑d for "sanctifying us with His commandments and commanding us to..." Nevertheless, the individual rabbinic precepts are not counted as part of the 613 (and, are considered "rabbinic," a classification that has certain halachic implications).

Principle 2

Do not include laws which are derived from one of the Thirteen Principles of Torah Exegesis.

Every word and letter in the Torah is exact, and the Sages extrapolated many laws from an extra (or missing) word or letter, or a particular sequence which the Torah chooses to use (click here for more on this topic). Nevertheless, unless the Sages explicitly say that a particular law that they derived is categorized as biblical, it is not counted as part of the 613.

An example of this is the obligation to accord honor to parents-in-law, a precept derived from an extra word ("et") in a verse. Though the Torah alludes to the concept, it is not considered a biblical command.

Principle 3

Do not count mitzvot which are not binding on all generations. E.g., the laws regarding the disassembly of the Tabernacle, or the prohibition against waging war on Amon and Moab, which only applied to the Israelites in the desert.

Principle 4

We do not include "encompassing" directives in the count. E.g., "And keep My covenant" (Exodus 19:5), or "Concerning all that I have said to you, you shall beware..." (ibid. 22:30), or "And you shall be a holy people to Me" (ibid. 23:23).

Verses that don't instruct us regarding a specific action, but regarding the imperative to observe all of the Torah's commandments, are not included in the 613.

Principle 5

Sefer Hamitzvot (Abridged and Adapted)

An abbreviated rendition of Maimonides' Sefer Hamitzvot

The reason for a mitzvah is not counted on its own.

At times, the Torah tells us the reason for a command in language that could be understood as an independent precept—when in fact it is simply the rationale behind the words that precede it.

For example, "He shall not leave the Sanctuary, and he shall not desecrate the holy things of his G‑d" (Leviticus 21:12). Not desecrating the holy is not a commandment on its own, rather it is the reason why the Kohen may not leave the sanctuary. Or, "Her first husband, who had sent her away, may not take her again to be his wife...and you shall not bring sin to the land" (Deuteronomy 24:4). Here, too, "bringing sin to the land" is not an independent prohibition, but the reason why one may not remarry his divorced wife if she has remarried in the interim.

Principle 6

A mitzvah that has both negative and positive components is counted as two—one Positive Commandment and one Negative Commandment.

E.g., we are commanded to rest on Shabbat and desist from work on the Shabbat. We are commanded to "afflict" ourselves on Yom Kippur and we are commanded not to eat on this holy day. Though a transgression of one is also a transgression of the other – if you eat on Yom Kippur you have not afflicted yourself; if you work on Shabbat you have not rested – nevertheless these are considered two independent mitzvot.

Principle 7

The different applications of a mitzvah are not individually counted.

E.g., one who inadvertently defiles the Temple or holy foods is required to bring a sin offering (Leviticus 5). If his financial situation allows, he is to bring a sheep or she-goat; otherwise he brings two birds; and if he is completely impoverished, he brings a flour offering. All this, however, is counted as one mitzvah—the mitzvah of bringing a sin offering when this particular offense is committed—although the execution of the mitzvah varies depending on the situation.

Principle 8

Do not count a negative statement amongst the prohibitions.

The Hebrew word "lo" can mean both "do not" and "shall not"; and only the "do not"s are counted as prohibitions. The only way to discern between the two is by studying the context of the word.

Examples: "She shall not go free as the slaves go free" (Exodus 21:7). This verse should not be construed as a prohibition; it is simply telling us that the circumstances that mandate the emancipation of a Canaanite slave do not apply to a Hebrew maidservant. Certainly, however, if the owner wishes to free her, he may do so.

Or, "So he shall not be like Korach and his company" (Numbers 17:5). This is not a prohibition, rather a warning that anyone who dares contest the priesthood of Aaron's descendents will meet the same fate as Korach and his cohorts.

Principle 9

Do not count the number of times a commandment is mentioned in the Torah, only the act which is prohibited or commanded.

Certain commandments are repeated in the Torah numerous times. For example, the commandment to rest on Shabbat is mentioned twelve times and the prohibition against consuming blood is repeated no less than seven times. Nevertheless, when counting the 613 mitzvot, we only count a prohibited or prescribed act once.

(The exception to this rule is those instances where the Sages have deduced that the repetition of a particular commandment is intended to prohibit or instruct us regarding a different act. In such a case, the [seemingly] repetitive verse is counted as a separate mitzvah—for it is in fact instructing us regarding something different than the first verse.)

It should be noted that though we count the prohibited acts, and not the amount of times mentioned, we only count prohibited acts individually specified in the Torah. At times, the Torah will issue a prohibition employing general terminology, for this prohibition includes multiple acts. For example, "You shall not eat over the blood" (Leviticus 19:26). This prohibition teaches us not to eat sacrificial flesh before the blood is sprinkled on the altar, not to eat from any animal before its soul (contained in its blood) has fully departed, that the members of a court may not eat on the day that they implement a capital verdict, and more. Though all these are biblically forbidden, none are counted as part of the 613—as none of them are mentioned specifically in the Torah.

Principle 10

Do not count a preparatory act as an independent mitzvah.

E.g., "You shall take fine flour and bake it [into] twelve loaves" (Leviticus 24:5). This is not an independent mitzvah, but a necessary prerequisite to the mitzvah of placing Showbreads on the Table in the Temple's sanctuary. Similarly, "Command the children of Israel, and they shall take to you pure olive oil" (ibid. 27:2) is not counted as one of the 613 mitzvot, rather it is a preamble to the mitzvah of kindling the Temple Menorah daily.

Principle 11

If a mitzvah is comprised of a number of elements, do not count them separately.

E.g., "And you shall take for yourselves on the first day [of Sukkot], the fruit of a beautiful tree, date palm fronds, a branch of a braided tree, and willows of the brook" (ibid. 23:40). All these individual elements come together to create a single mitzvah—the mitzvah of taking the Four Species. As such, they are collectively counted as only one mitzvah.

Principle 12

When commanded to do a certain action, do not count each part of the action separately.

E.g., "They shall make Me a sanctuary" (Exodus 25:8). There's a general mitzvah to construct a sanctuary for G‑d. For this purpose, it is necessary to construct an Ark, a Menorah, altars, etc.—but these are all details of the overarching mitzvah of creating a sanctuary for G‑d.

Principle 13

We do not count the amount of days a mitzvah is performed.

E.g., we are commanded to dwell in a sukkah during the seven days of the holiday of Sukkot—yet this is one mitzvah. We are commanded to bring a special offering in the Temple on Rosh Chodesh—yet this is one mitzvah, not twelve. We are commanded to make pilgrimage to the Temple thrice yearly—but this is one mitzvah, the mitzvah of pilgrimage.

Principle 14

We do not count the punishment administered for each transgression.

The Torah specifies many forms of punishments that the courts administer: Four types of capital punishment, corporal punishment, financial remuneration, sacrificial penalties, etc.

While each form of punishment constitutes an independent mitzvah, we do not count the penalty for a particular transgression as part of the 613. For example, there are many different transgressions that mandate the bringing of a sin-offering. Yet, the bringing of a sin-offering is counted as only one mitzvah.