diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
index 6415493b37..5d424676bb 100644
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -890,7 +890,7 @@ void DrawEngineList(VehicleType type, int l, int r, int y, const GUIEngineList *
 	int count_width = 0;
 	if (show_count) {
 		replace_icon = GetSpriteSize(SPR_GROUP_REPLACE_ACTIVE);
-		SetDParam(0, 999);
+		SetDParamMaxDigits(0, 3);
 		count_width = GetStringBoundingBox(STR_TINY_BLACK_COMA).width;
 	}
 
diff --git a/src/cheat_gui.cpp b/src/cheat_gui.cpp
index 18901c5dab..6b37079bd3 100644
--- a/src/cheat_gui.cpp
+++ b/src/cheat_gui.cpp
@@ -259,7 +259,7 @@ struct CheatWindow : Window {
 
 						/* Draw coloured flag for change company cheat */
 						case STR_CHEAT_CHANGE_COMPANY:
-							SetDParam(0, 15);
+							SetDParamMaxValue(0, MAX_COMPANIES);
 							width = max(width, GetStringBoundingBox(ce->str).width + 10 + 10);
 							break;
 
diff --git a/src/company_gui.cpp b/src/company_gui.cpp
index ae6f394e97..c6ddd6bd0b 100644
--- a/src/company_gui.cpp
+++ b/src/company_gui.cpp
@@ -319,7 +319,7 @@ struct CompanyFinancesWindow : Window {
 			case WID_CF_BALANCE_VALUE:
 			case WID_CF_LOAN_VALUE:
 			case WID_CF_TOTAL_VALUE:
-				SetDParam(0, CompanyFinancesWindow::max_money);
+				SetDParamMaxValue(0, CompanyFinancesWindow::max_money);
 				size->width = max(GetStringBoundingBox(STR_FINANCES_NEGATIVE_INCOME).width, GetStringBoundingBox(STR_FINANCES_POSITIVE_INCOME).width) + padding.width;
 				break;
 
@@ -1691,12 +1691,12 @@ struct CompanyInfrastructureWindow : Window
 				max_val = max(max_val, c->infrastructure.airport);
 				max_cost = max(max_cost, AirportMaintenanceCost(c->index));
 
-				SetDParam(0, max_val);
-				SetDParam(1, max_cost * 12); // Convert to per year
+				SetDParamMaxValue(0, max_val);
+				SetDParamMaxValue(1, max_cost * 12); // Convert to per year
 				size->width = max(size->width, GetStringBoundingBox(_settings_game.economy.infrastructure_maintenance ? STR_COMPANY_INFRASTRUCTURE_VIEW_COST : STR_WHITE_COMMA).width + 20); // Reserve some wiggle room.
 
 				if (_settings_game.economy.infrastructure_maintenance) {
-					SetDParam(0, this->GetTotalMaintenanceCost() * 12); // Convert to per year
+					SetDParamMaxValue(0, this->GetTotalMaintenanceCost() * 12); // Convert to per year
 					this->total_width = GetStringBoundingBox(STR_COMPANY_INFRASTRUCTURE_VIEW_TOTAL).width + 20;
 					size->width = max(size->width, this->total_width);
 				}
@@ -2095,14 +2095,14 @@ struct CompanyWindow : Window
 				break;
 
 			case WID_C_DESC_VEHICLE_COUNTS:
-				SetDParam(0, 5000); // Maximum number of vehicles
+				SetDParamMaxValue(0, 5000); // Maximum number of vehicles
 				for (uint i = 0; i < lengthof(_company_view_vehicle_count_strings); i++) {
 					size->width = max(size->width, GetStringBoundingBox(_company_view_vehicle_count_strings[i]).width);
 				}
 				break;
 
 			case WID_C_DESC_INFRASTRUCTURE_COUNTS:
-				SetDParam(0, UINT_MAX);
+				SetDParamMaxValue(0, UINT_MAX);
 				size->width = max(size->width, GetStringBoundingBox(STR_COMPANY_VIEW_INFRASTRUCTURE_RAIL).width);
 				size->width = max(size->width, GetStringBoundingBox(STR_COMPANY_VIEW_INFRASTRUCTURE_ROAD).width);
 				size->width = max(size->width, GetStringBoundingBox(STR_COMPANY_VIEW_INFRASTRUCTURE_WATER).width);
@@ -2115,7 +2115,7 @@ struct CompanyWindow : Window
 				const Company *c2;
 
 				FOR_ALL_COMPANIES(c2) {
-					SetDParam(0, 25);
+					SetDParamMaxValue(0, 75);
 					SetDParam(1, c2->index);
 
 					size->width = max(size->width, GetStringBoundingBox(STR_COMPANY_VIEW_SHARES_OWNED_BY).width);
diff --git a/src/date_gui.cpp b/src/date_gui.cpp
index 3162a4ef99..b2421556ce 100644
--- a/src/date_gui.cpp
+++ b/src/date_gui.cpp
@@ -117,10 +117,8 @@ struct SetDateWindow : Window {
 				break;
 
 			case WID_SD_YEAR:
-				for (Year i = this->min_year; i <= this->max_year; i++) {
-					SetDParam(0, i);
-					d = maxdim(d, GetStringBoundingBox(STR_JUST_INT));
-				}
+				SetDParamMaxValue(0, this->max_year);
+				d = maxdim(d, GetStringBoundingBox(STR_JUST_INT));
 				break;
 		}
 
diff --git a/src/depot_gui.cpp b/src/depot_gui.cpp
index 758c5f5af5..25d36b690c 100644
--- a/src/depot_gui.cpp
+++ b/src/depot_gui.cpp
@@ -579,7 +579,7 @@ struct DepotWindow : Window {
 				uint min_height = 0;
 
 				if (this->type == VEH_TRAIN) {
-					SetDParam(0, 1000);
+					SetDParamMaxValue(0, 1000);
 					SetDParam(1, 1);
 					this->count_width = GetStringBoundingBox(STR_TINY_BLACK_DECIMAL).width + WD_FRAMERECT_LEFT + WD_FRAMERECT_RIGHT;
 				} else {
diff --git a/src/genworld_gui.cpp b/src/genworld_gui.cpp
index ba1a95df3d..1666a48034 100644
--- a/src/genworld_gui.cpp
+++ b/src/genworld_gui.cpp
@@ -449,12 +449,12 @@ struct GenerateLandscapeWindow : public Window {
 
 			case WID_GL_MAPSIZE_X_PULLDOWN:
 			case WID_GL_MAPSIZE_Y_PULLDOWN:
-				SetDParam(0, MAX_MAP_SIZE);
+				SetDParamMaxValue(0, MAX_MAP_SIZE);
 				*size = GetStringBoundingBox(STR_JUST_INT);
 				break;
 
 			case WID_GL_SNOW_LEVEL_TEXT:
-				SetDParam(0, MAX_TILE_HEIGHT);
+				SetDParamMaxValue(0, MAX_TILE_HEIGHT);
 				*size = GetStringBoundingBox(STR_JUST_INT);
 				break;
 
@@ -466,7 +466,7 @@ struct GenerateLandscapeWindow : public Window {
 
 			case WID_GL_TOWN_PULLDOWN:
 				strs = _num_towns;
-				SetDParam(0, CUSTOM_TOWN_MAX_NUMBER);
+				SetDParamMaxValue(0, CUSTOM_TOWN_MAX_NUMBER);
 				*size = GetStringBoundingBox(STR_NUM_CUSTOM_NUMBER);
 				break;
 
@@ -476,7 +476,7 @@ struct GenerateLandscapeWindow : public Window {
 			case WID_GL_TERRAIN_PULLDOWN:    strs = _elevations; break;
 			case WID_GL_WATER_PULLDOWN:
 				strs = _sea_lakes;
-				SetDParam(0, CUSTOM_SEA_LEVEL_MAX_PERCENTAGE);
+				SetDParamMaxValue(0, CUSTOM_SEA_LEVEL_MAX_PERCENTAGE);
 				*size = GetStringBoundingBox(STR_SEA_LEVEL_CUSTOM_PERCENTAGE);
 				break;
 
@@ -923,11 +923,11 @@ struct CreateScenarioWindow : public Window
 
 			case WID_CS_MAPSIZE_X_PULLDOWN:
 			case WID_CS_MAPSIZE_Y_PULLDOWN:
-				SetDParam(0, MAX_MAP_SIZE);
+				SetDParamMaxValue(0, MAX_MAP_SIZE);
 				break;
 
 			case WID_CS_FLAT_LAND_HEIGHT_TEXT:
-				SetDParam(0, MAX_TILE_HEIGHT);
+				SetDParamMaxValue(0, MAX_TILE_HEIGHT);
 				break;
 
 			default:
@@ -1194,7 +1194,7 @@ struct GenerateProgressWindow : public Window {
 	{
 		switch (widget) {
 			case WID_GP_PROGRESS_BAR: {
-				SetDParam(0, 100);
+				SetDParamMaxValue(0, 100);
 				*size = GetStringBoundingBox(STR_GENERATION_PROGRESS);
 				/* We need some spacing for the 'border' */
 				size->height += 8;
diff --git a/src/graph_gui.cpp b/src/graph_gui.cpp
index 0d87bba00c..82d862d33f 100644
--- a/src/graph_gui.cpp
+++ b/src/graph_gui.cpp
@@ -504,7 +504,7 @@ public:
 			}
 		} else {
 			/* Draw the label under the data point rather than on the grid line. */
-			SetDParam(0, this->x_values_start + this->num_on_x_axis * this->x_values_increment);
+			SetDParamMaxValue(0, this->x_values_start + this->num_on_x_axis * this->x_values_increment);
 			x_label_width = GetStringBoundingBox(STR_GRAPH_Y_LABEL_NUMBER).width;
 		}
 
@@ -1322,10 +1322,10 @@ struct PerformanceRatingDetailWindow : Window {
 				for (uint i = SCORE_BEGIN; i < SCORE_END; i++) {
 					score_info_width = max(score_info_width, GetStringBoundingBox(STR_PERFORMANCE_DETAIL_VEHICLES + i).width);
 				}
-				SetDParam(0, 1000);
+				SetDParamMaxValue(0, 1000);
 				score_info_width += GetStringBoundingBox(STR_BLACK_COMMA).width + WD_FRAMERECT_LEFT;
 
-				SetDParam(0, 100);
+				SetDParamMaxValue(0, 100);
 				this->bar_width = GetStringBoundingBox(STR_PERFORMANCE_DETAIL_PERCENT).width + 20; // Wide bars!
 
 				/* At this number we are roughly at the max; it can become wider,
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
index bbb6e9d0eb..3996ddc187 100644
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -182,7 +182,7 @@ private:
 		}
 		this->tiny_step_height = max(this->tiny_step_height, this->column_size[VGC_PROFIT].height);
 
-		SetDParam(0, GroupStatistics::Get(this->vli.company, ALL_GROUP, this->vli.vtype).num_vehicle > 900 ? 9999 : 999);
+		SetDParamMaxValue(0, GroupStatistics::Get(this->vli.company, ALL_GROUP, this->vli.vtype).num_vehicle, 3);
 		this->column_size[VGC_NUMBER] = GetStringBoundingBox(STR_TINY_COMMA);
 		this->tiny_step_height = max(this->tiny_step_height, this->column_size[VGC_NUMBER].height);
 
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
index 55dc817614..c0a73d8080 100644
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -526,24 +526,24 @@ public:
 
 			case WID_NG_CLIENTS:
 				size->width += 2 * WD_SORTBUTTON_ARROW_WIDTH; // Make space for the arrow
-				SetDParam(0, MAX_CLIENTS);
-				SetDParam(1, MAX_CLIENTS);
-				SetDParam(2, MAX_COMPANIES);
-				SetDParam(3, MAX_COMPANIES);
+				SetDParamMaxValue(0, MAX_CLIENTS);
+				SetDParamMaxValue(1, MAX_CLIENTS);
+				SetDParamMaxValue(2, MAX_COMPANIES);
+				SetDParamMaxValue(3, MAX_COMPANIES);
 				*size = maxdim(*size, GetStringBoundingBox(STR_NETWORK_SERVER_LIST_GENERAL_ONLINE));
 				break;
 
 			case WID_NG_MAPSIZE:
 				size->width += 2 * WD_SORTBUTTON_ARROW_WIDTH; // Make space for the arrow
-				SetDParam(0, MAX_MAP_SIZE);
-				SetDParam(1, MAX_MAP_SIZE);
+				SetDParamMaxValue(0, MAX_MAP_SIZE);
+				SetDParamMaxValue(1, MAX_MAP_SIZE);
 				*size = maxdim(*size, GetStringBoundingBox(STR_NETWORK_SERVER_LIST_MAP_SIZE_SHORT));
 				break;
 
 			case WID_NG_DATE:
 			case WID_NG_YEARS:
 				size->width += 2 * WD_SORTBUTTON_ARROW_WIDTH; // Make space for the arrow
-				SetDParam(0, 99999);
+				SetDParamMaxValue(0, 5);
 				*size = maxdim(*size, GetStringBoundingBox(STR_JUST_INT));
 				break;
 
@@ -2071,12 +2071,12 @@ struct NetworkJoinStatusWindow : Window {
 		}
 
 		/* For the number of waiting (other) players */
-		SetDParam(0, MAX_CLIENTS);
+		SetDParamMaxValue(0, MAX_CLIENTS);
 		width = max(width, GetStringBoundingBox(STR_NETWORK_CONNECTING_WAITING).width);
 
 		/* Account for downloading ~ 10 MiB */
-		SetDParam(0, 10000000);
-		SetDParam(1, 10000000);
+		SetDParamMaxDigits(0, 8);
+		SetDParamMaxDigits(1, 8);
 		width = max(width, GetStringBoundingBox(STR_NETWORK_CONNECTING_DOWNLOADING_1).width);
 		width = max(width, GetStringBoundingBox(STR_NETWORK_CONNECTING_DOWNLOADING_2).width);
 
diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
index bcdaa8db86..e052cc19c5 100644
--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@@ -197,7 +197,7 @@ struct NewGRFParametersWindow : public Window {
 			}
 
 			case WID_NP_NUMPAR: {
-				SetDParam(0, 999);
+				SetDParamMaxValue(0, lengthof(this->grf_config->param));
 				Dimension d = GetStringBoundingBox(this->GetWidget<NWidgetCore>(widget)->widget_data);
 				d.width += padding.width;
 				d.height += padding.height;
@@ -1965,7 +1965,7 @@ struct ScanProgressWindow : public Window {
 	{
 		switch (widget) {
 			case WID_SP_PROGRESS_BAR: {
-				SetDParam(0, 100);
+				SetDParamMaxValue(0, 100);
 				*size = GetStringBoundingBox(STR_GENERATION_PROGRESS);
 				/* We need some spacing for the 'border' */
 				size->height += 8;
@@ -1974,8 +1974,8 @@ struct ScanProgressWindow : public Window {
 			}
 
 			case WID_SP_PROGRESS_TEXT:
-				SetDParam(0, 9999);
-				SetDParam(1, 9999);
+				SetDParamMaxDigits(0, 4);
+				SetDParamMaxDigits(1, 4);
 				/* We really don't know the width. We could determine it by scanning the NewGRFs,
 				 * but this is the status window for scanning them... */
 				size->width = max(400U, GetStringBoundingBox(STR_NEWGRF_SCAN_STATUS).width);
diff --git a/src/order_gui.cpp b/src/order_gui.cpp
index f50ef73ed1..85bd196ef4 100644
--- a/src/order_gui.cpp
+++ b/src/order_gui.cpp
@@ -1097,7 +1097,7 @@ public:
 		if (widget != WID_O_ORDER_LIST) return;
 
 		bool rtl = _current_text_dir == TD_RTL;
-		SetDParam(0, 99);
+		SetDParamMaxValue(0, this->vehicle->GetNumOrders(), 2);
 		int index_column_width = GetStringBoundingBox(STR_ORDER_INDEX).width + 2 * GetSpriteSize(rtl ? SPR_ARROW_RIGHT : SPR_ARROW_LEFT).width + 3;
 		int middle = rtl ? r.right - WD_FRAMETEXT_RIGHT - index_column_width : r.left + WD_FRAMETEXT_LEFT + index_column_width;
 
diff --git a/src/signs_gui.cpp b/src/signs_gui.cpp
index 0f2d316905..120906ae9e 100644
--- a/src/signs_gui.cpp
+++ b/src/signs_gui.cpp
@@ -274,7 +274,7 @@ struct SignListWindow : Window, SignList {
 			}
 
 			case WID_SIL_CAPTION:
-				SetDParam(0, max<size_t>(1000, Sign::GetPoolSize()));
+				SetDParamMaxValue(0, Sign::GetPoolSize(), 3);
 				*size = GetStringBoundingBox(STR_SIGN_LIST_CAPTION);
 				size->height += padding.height;
 				size->width  += padding.width;
diff --git a/src/statusbar_gui.cpp b/src/statusbar_gui.cpp
index 4a014d2613..f8d39ceaf4 100644
--- a/src/statusbar_gui.cpp
+++ b/src/statusbar_gui.cpp
@@ -104,7 +104,7 @@ struct StatusBarWindow : Window {
 		Dimension d;
 		switch (widget) {
 			case WID_S_LEFT:
-				SetDParam(0, MAX_YEAR * DAYS_IN_YEAR);
+				SetDParamMaxValue(0, MAX_YEAR * DAYS_IN_YEAR);
 				d = GetStringBoundingBox(STR_WHITE_DATE_LONG);
 				break;
 
diff --git a/src/strings.cpp b/src/strings.cpp
index 12f41e1588..a8a7cc62b6 100644
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -90,6 +90,38 @@ void StringParameters::ShiftParameters(uint amount)
 	MemMoveT(this->data + amount, this->data, this->num_param - amount);
 }
 
+/**
+ * Set DParam n to some number that is suitable for string size computations.
+ * @param n Index of the string parameter.
+ * @param max_value The biggest value which shall be displayed.
+ *                  For the result only the number of digits of \a max_value matter.
+ * @param min_count Minimum number of digits indepentent of \a max.
+ */
+void SetDParamMaxValue(uint n, uint64 max_value, uint min_count)
+{
+	uint num_digits = 1;
+	while (max_value >= 10) {
+		num_digits++;
+		max_value /= 10;
+	}
+	SetDParamMaxDigits(n, max(min_count, num_digits));
+}
+
+/**
+ * Set DParam n to some number that is suitable for string size computations.
+ * @param n Index of the string parameter.
+ * @param count Number of digits which shall be displayable.
+ */
+void SetDParamMaxDigits(uint n, uint count)
+{
+	static const uint biggest_digit = 8; ///< Digit with the biggest string width.
+	uint64 val = biggest_digit;
+	for (; count > 1; count--) {
+		val = 10 * val + biggest_digit;
+	}
+	SetDParam(n, val);
+}
+
 /**
  * Copy \a num string parameters from array \a src into the global string parameter array.
  * @param offs Index in the global array to copy the first string parameter to.
diff --git a/src/strings_func.h b/src/strings_func.h
index 395a80e1a1..f977b3b3cd 100644
--- a/src/strings_func.h
+++ b/src/strings_func.h
@@ -155,6 +155,9 @@ static inline void SetDParam(uint n, uint64 v)
 	_global_string_params.SetParam(n, v);
 }
 
+void SetDParamMaxValue(uint n, uint64 max_value, uint min_count = 0);
+void SetDParamMaxDigits(uint n, uint count);
+
 void SetDParamStr(uint n, const char *str);
 
 void CopyInDParam(int offs, const uint64 *src, int num);
diff --git a/src/timetable_gui.cpp b/src/timetable_gui.cpp
index 272682eb17..6533e351d5 100644
--- a/src/timetable_gui.cpp
+++ b/src/timetable_gui.cpp
@@ -200,7 +200,7 @@ struct TimetableWindow : Window {
 	{
 		switch (widget) {
 			case WID_VT_ARRIVAL_DEPARTURE_PANEL:
-				SetDParam(0, MAX_YEAR * DAYS_IN_YEAR);
+				SetDParamMaxValue(0, MAX_YEAR * DAYS_IN_YEAR);
 				this->deparr_time_width = GetStringBoundingBox(STR_JUST_DATE_TINY).width;
 				this->deparr_abbr_width = max(GetStringBoundingBox(STR_TIMETABLE_ARRIVAL_ABBREVIATION).width, GetStringBoundingBox(STR_TIMETABLE_DEPARTURE_ABBREVIATION).width);
 				size->width = WD_FRAMERECT_LEFT + this->deparr_abbr_width + 10 + this->deparr_time_width + WD_FRAMERECT_RIGHT;
@@ -368,7 +368,7 @@ struct TimetableWindow : Window {
 				bool final_order = false;
 
 				bool rtl = _current_text_dir == TD_RTL;
-				SetDParam(0, 99);
+				SetDParamMaxValue(0, v->GetNumOrders(), 2);
 				int index_column_width = GetStringBoundingBox(STR_ORDER_INDEX).width + 2 * GetSpriteSize(rtl ? SPR_ARROW_RIGHT : SPR_ARROW_LEFT).width + 3;
 				int middle = rtl ? r.right - WD_FRAMERECT_RIGHT - index_column_width : r.left + WD_FRAMERECT_LEFT + index_column_width;
 
diff --git a/src/town_gui.cpp b/src/town_gui.cpp
index ad9ee06056..490bca5ed9 100644
--- a/src/town_gui.cpp
+++ b/src/town_gui.cpp
@@ -780,7 +780,7 @@ public:
 					assert(t != NULL);
 
 					SetDParam(0, t->index);
-					SetDParam(1, 10000000); // 10^7
+					SetDParamMaxDigits(1, 8);
 					d = maxdim(d, GetStringBoundingBox(STR_TOWN_DIRECTORY_TOWN));
 				}
 				Dimension icon_size = GetSpriteSize(SPR_TOWN_RATING_GOOD);
@@ -794,7 +794,7 @@ public:
 				break;
 			}
 			case WID_TD_WORLD_POPULATION: {
-				SetDParam(0, 1000000000); // 10^9
+				SetDParamMaxDigits(0, 10);
 				Dimension d = GetStringBoundingBox(STR_TOWN_POPULATION);
 				d.width += padding.width;
 				d.height += padding.height;
diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
index d939375866..f64a3cc473 100644
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -1805,7 +1805,7 @@ struct VehicleDetailsWindow : Window {
 				Dimension dim = { 0, 0 };
 				size->height = WD_FRAMERECT_TOP + 4 * FONT_HEIGHT_NORMAL + WD_FRAMERECT_BOTTOM;
 
-				for (uint i = 0; i < 4; i++) SetDParam(i, INT16_MAX);
+				for (uint i = 0; i < 4; i++) SetDParamMaxValue(i, INT16_MAX);
 				static const StringID info_strings[] = {
 					STR_VEHICLE_INFO_MAX_SPEED,
 					STR_VEHICLE_INFO_WEIGHT_POWER_MAX_SPEED,
@@ -1849,8 +1849,8 @@ struct VehicleDetailsWindow : Window {
 				break;
 
 			case WID_VD_SERVICING_INTERVAL:
-				SetDParam(0, 9999); // Roughly the maximum interval
-				SetDParam(1, MAX_YEAR * DAYS_IN_YEAR); // Roughly the maximum year
+				SetDParamMaxValue(0, MAX_SERVINT_DAYS); // Roughly the maximum interval
+				SetDParamMaxValue(1, MAX_YEAR * DAYS_IN_YEAR); // Roughly the maximum year
 				size->width = max(GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_PERCENT).width, GetStringBoundingBox(STR_VEHICLE_DETAILS_SERVICING_INTERVAL_DAYS).width) + WD_FRAMERECT_LEFT + WD_FRAMERECT_RIGHT;
 				size->height = WD_FRAMERECT_TOP + FONT_HEIGHT_NORMAL + WD_FRAMERECT_BOTTOM;
 				break;