The current price of a first-class stamp in the UK is £1.70 for a standard letter up to 100g and within the size limits of 24cm x 16.5cm x 5mm

. This price took effect on April 7, 2025, following a 5p increase from £1.65, which was the price since October 2024

. For larger letters up to 100g (35.3cm x 25cm x 2.5cm), the first-class stamp costs £3.15

. In the United States, a First-Class Mail Forever® stamp costs $0.73 for a standard 1 oz letter, and this stamp will remain valid even if postage rates increase in the future

. To summarize:

Country| First-Class Stamp Price| Details
---|---|---
UK| £1.70| Standard letter up to 100g, 24cm x 16.5cm x 5mm, price effective April 2025
UK| £3.15| Larger letters up to 100g, 35.3cm x 25cm x 2.5cm
USA| $0.73| Standard 1 oz letter, Forever® stamp

This reflects the most recent official postage rates as of May 2025.