How much is a Peruta?
The Peruta was the smallest form of currency in the times of the Mishna and Talmud. It was a copper coin. Its silver worth is the weight of half a barley, which is about .025 grams. Thus, the worth of a Peruta is 0.025 of a gram of silver [1/40th of a gram]. In accordance to the current price of silver [$0.54 per gram-January 2017] the worth of a Peruta is 1.35 cents or 6 [5.1] Agurot. One must periodically verify anew as to the worth of silver, in order to know the current price of a Peruta. Some Rabbanim of today hold that one must also include the amount of sales tax levied on purchasing this amount of silver in his country [i.e. 17% in Israel, in U.S.A. depends on your state]. Furthermore, some Poskim question that perhaps a Peruta must contain an amount that one can use to purchase a substantial item in one’s country, such as many fruits, and thus the above-mentioned minuscule amount is no longer accurate for today’s times. Practically, there is room for one to be stringent like this opinion.
Areas in Halacha that a Peruta is relevant:
In Halacha, less than a Peruta is not considered money, and a value dependent Mitzvah cannot be fulfilled when using less than a Peruta. The following are some areas in Halacha in which a Peruta’s worth is relevant.
- Tzedaka: One who is careful to give money to charity each day prior to Davening is to give at least a Peruta’s worth. The same applies prior to candle lighting.
- Matanos Laevyonim: The minimum value one must give a pauper to fulfill the Mitzvah of Matanos Laevyonim is a Peruta.
- Pidyon Maaser Sheiyni: Maaser Sheiyni is redeemed onto a Peruta.
- Kiddushin: One may only marry a woman with an item worth a Peruta or more. If the item is worth less than a Peruta she remains single.
- Moda Bemiktzas: One who admits to a partial claim is only liable for a swear if he admitted to being liable for at least a Peruta’s worth of debt.
 Shiurei Torah 3/42
 Shiureiy Torah ibid in name of Rambam; Rif; Ran in name of Geonim; Rabbeinu Chananel Shavuos 39b; Rosh Bechoros 8; Michaber Y.D. 331/133; E.H. 27; C.M. 88
 Smeh C.M. 88/2 concludes with Tzaruch Iyun; Shach Y.D. 294/16 in quote of Smeh; Tiferes Yisrael Shavuos 6/1 negates this opinion of Smeh, however Shiureiy Torah ibid p. 283 defends the ruling of Smeh concluding “It is a great Sevara to say that the Biblical Peruta has now lost its value” See Nitei Gavriel Purim 65/1 that today in the USA a Peruta is no less than 5 cents and in Israel 10 Agurot.
How much is the Peruta worth today according to this opinion? Shiureiy Torah ibid concludes that a Peruta according to the Smeh/Shach is the amount of money in the country needed to purchase 20 grams of bread. In today’s time this equals approximately 15 Agurot.
 Shiureiy Torah ibid “It is a great Sevara to say that the Biblical Peruta has now lost its value… One who desires to be stringent as rules the Smeh and Shach…”
 See Igros Kodesh 11/18 “A Peruta or two” [printed in Shulchan Menachem 1/151]
 Ritva Megillah brought in M”B 694/2; Kaf Hachaim 694/7; See Ashel Avraham Butchach 695; The Peri Megadim [brought in M”B 694/2] writes he has not found an amount written anywhere.
Other Opinions: Some Poskim rule that the present must contain a minimum worth of three Kibeitzim of food [165 grams]. [Zera Yaakov 11 brought in Machazikei Bracha 694/2; Shaareiy Teshuvah 694/1; Ben Ish Chaiy Titzaveh 15; Kaf Hachaim 694/7 and 11; Meiy Yehuda 86; Pekudas Eliezer ibid] Other Poskim rule it must contain a Kebeitza worth. [Tzafnas Paneiach on Rambam Megillah 2/15] Other Poskim rule it is to be the size of one Grogeres [Pischeiy Teshuvah 694 based on Rama Y.D. 249/4] Other opinions rule it must be a present of importance. [Maharsha Megillah 7b]
 Michaber Y.D. 131/133
 Michaber E.H. 31/1
 Michaber C.M. 88/1