Find out exactly how many Forever stamps you need for any letter, postcard, or large envelope.
Standard letter with 1-4 sheets is about 1 oz.
Approximate, using 20 lb paper + envelope.
Accuracy note: Large-envelope additional-ounce pricing assumes the standard $0.29 per extra ounce. Based on USPS retail prices, January 18, 2026 rates (checked August 2026).
