Turkish Airlines operates two different baggage charging policies depending on where your flight is from/to - a kilo concept and a piece concept.
The free baggage allowance, and hence excess baggage charge is calculated under the piece concept only if you fly from/to the following places:
The baggage piece concept applies to flights to and from Angola, Argentina, Benin , Burkina Faso, Cameroon, Canada, Chad, Colombia, Cuba, Democratic Republic of Congo, Gabon, Ghana, Guinea, Ivory Coast, Japan, Madagascar, Mali, Mauritania, Mauritius, Niger, Nigeria, Panama, Senegal, the Seychelles, Sierra Leone, South America, Sudan, the United States of America, and Venezuela.
Since neither your origin or destination fall into this list, the kilo (weight) concept applies.
This page details the excess baggage charges:
- Your departure airport London is in region 4 and the destination airport Dar es Salaam is in region 5 (see table 1).
- The charge for 1kg excess baggage between regions 4 and 5 is €27 (see table 2).
So if all your luggage together weighs e.g. 55kg (the number of pieces is not relevant) and the allowance is 30kg, you will pay €675 for 25kg excess baggage.