The name Sienna in Hebrew letters is סינה. Below: how its number adds up, which page of the Torah it falls on and what verse stands there. Everything is computed, nothing is guessed.
סינה
In short
Your name in Hebrew letters is סינה. Adding up the numbers of its letters gives 125 — the same as the Torah word ענה, “to answer, afflict”. That number points to Torah page 125 of 354 — in the portion Yitro. What that portion is about: Jethro's counsel on judges; standing at Sinai; the Ten Utterances; “you shall not make yourself an idol”. The verse that begins with the first letter of your name and ends with the last is Numbers 14:19. Each of these steps is laid out below with its sources. Every figure can be checked by hand.
You wrote “Sienna” — this exact spelling is what was calculated: סינה. A name from the Tanakh — its Tanakh spelling is used. If your name is spelled differently, correct the Hebrew spelling and the report is recomputed.
Adding up the letters of the name סינה gives 125.
125
The number 125 is the Torah word ענה — «to answer, afflict» (Genesis 18:27).
And HaShem said unto Moses: 'Go down, charge the people, lest they break through unto HaShem to gaze, and many of them perish.
This is from the portion Yitro. What it is about: Jethro's counsel on judges; standing at Sinai; the Ten Utterances; “you shall not make yourself an idol”.
The same number, 125, is given by these Tanakh names:
Noa נעה
Other ways of counting
The tradition counts the same name in several ways. The main one is above: each letter is its number. The other eight are old and checkable too; each gives its own number, and many of them have a Torah word with the same number.
Final letters as 500–900 (mispar gadol) — 125. A Torah word with the same number is ענה — “to answer, afflict” (Genesis 18:27).
Reduced, each letter to one digit (mispar katan) — 17. A Torah word with the same number is טוב — “good” (Genesis 1:4).
Ordinal: alef 1, bet 2 … tav 22 (mispar siduri) — 44. A Torah word with the same number is ילד — “to bear, give birth” (Genesis 3:16).
Cumulative: a letter plus all letters before it (mispar kidmi) — 520. A Torah word with the same number is שכר — “wages, reward” (Genesis 15:1).
Squares of the letter values (mispar perati) — 6225.
Building: the sum grows with each letter (mispar bone’eh) — 375. A Torah word with the same number is עשה — “to do, make” (Genesis 1:7).
The letters that come out are חמטצ — not a word that stands in the Pentateuch. Atbash: letters mirrored, alef for tav, bet for shin, and the number of the resulting word — 147. A Torah word with the same number is צאנו — “his flock” (Genesis 4:4).
Filling: the names of the letters are counted — alef, bet, gimel… (milui) — 252. A Torah word with the same number is זמרה — “choice produce, song” (Genesis 43:11).
The number 125 appears in the classical books 10 times across 8 works. The earliest mention is ספר הפליאה (~1390).
Every letter of the name explained, the words and namesakes with references, the Hebrew date, the letter and tribe of the month, day 861 of your life (±1), the psalm by age, the attestations from the classical books — a PDF sent to your email.
The number of the day, every morning
Every date has a number too. Once a year it will match the number of your name — 125. The channel posts one number a day, one verse and the Torah page it lands on. Nothing after it, no mailing list.
Hebrew is written from right to left. סינה has 4 letters: ס Samekh, י Yod, נ Nun, ה He. The first letter is Samekh, the last is He.
For an engraving, a sign or a tattoo, show the spelling to someone who reads Hebrew: transliterating a name is a choice, not the only option.
The name סינה does not stand as a word in the Pentateuch — as with most names, including many Tanakh names from the later books.
The verse of your name
There is a custom: at the end of the prayer one says a Torah verse that begins with the first letter of one's name and ends with its last. For סינה these are ס and ה. The Pentateuch has exactly one such verse — Numbers 14:19:
סלח נא לעון העם הזה כגדל חסדך וכאשר נשאתה לעם הזה ממצרים ועד הנה
This is from the portion Shlach. What it is about: The twelve spies; forty years for forty days; challah and tzitzit.
Each Hebrew letter has a number; a word's number is their sum (alef 1 … tav 400). The page is the remainder modulo 354: the Torah divided into 354 pages of 861 letters, as the lunar year has 354 days. Everything can be checked by hand.