{ "openapi": "3.1.1", "info": { "title": "One-Rep-Max & Plate Loader API", "version": "1.0.0", "summary": "1RM from any set (7 formulas + average), % and RPE tables, and which plates to load.", "description": "Every endpoint performs the same calculation as the human page and returns inputs, result, units, assumptions, sources, warnings and computedAt. MCP endpoint: /mcp." }, "servers": [ { "url": "https://onerepmaxcalculator.usefulweb.site" } ], "paths": { "/api/v1/calculate": { "post": { "operationId": "calculate", "summary": "1RM from any set (7 formulas + average), % and RPE tables, and which plates to load.", "description": "Estimates your one-repetition maximum from the weight and reps of a set to failure (or with an RPE) with the Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner and Wathan equations and their average, prints a percentage table and an RPE table, and tells you which plates to put on each side of a kg or lb bar using only the plates you actually have.\n\nMethodology:\n- Seven published equations estimate the 1RM from the weight w and repetitions r to failure, as tabulated by LeSuer et al. (1997): Epley w(1 + 0.0333r); Brzycki 100w/(102.78 − 2.78r); Lander 100w/(101.3 − 2.67123r); Lombardi w·r^0.10; Mayhew 100w/(52.2 + 41.9e^(−0.055r)); O'Conner w(1 + 0.025r); Wathan 100w/(48.8 + 53.8e^(−0.075r)). The average of all seven is the headline estimate.\n- With 1 rep (and no RPE) the 1RM is the weight lifted.\n- RPE: reps in reserve = 10 − RPE are added to the reps (e.g. 5 reps at RPE 8 count as 7 reps to failure). The RPE table uses the same idea with the Epley relation %1RM = 1 ÷ (1 + 0.0333 × (reps + 10 − RPE)); it is derived, not a copy of a published RPE chart.\n- Percentage table: weight = % × average 1RM; the approximate reps at each percentage invert the Epley equation: reps = (1/% − 1) ÷ 0.0333.\n- Plate loader: per side = (target − bar − collars) ÷ 2. Plates are taken heaviest first (greedy) from the pairs you have; if that misses but an exact combination exists (possible with unusual plate sets), an exact subset-sum search finds the combination with the fewest plates. If the weight cannot be loaded exactly, the nearest loadable weights below and above are shown.", "tags": [ "calculators" ], "x-mcp-tool": "one_rep_max_calculator", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/OneRepMaxCalculatorInput" }, "examples": { "example1": { "summary": "100 kg × 5 reps, load 85%", "value": { "weight": 100, "reps": 5, "unit": "kg", "targetPercent": 85 } }, "example2": { "summary": "225 lb × 8 at RPE 8, load 275 lb", "value": { "weight": 225, "reps": 8, "unit": "lb", "rpe": 8, "targetWeight": 275 } }, "example3": { "summary": "Home gym: 62.5 kg with a 15 kg bar and few plates", "value": { "weight": 50, "reps": 10, "unit": "kg", "targetWeight": 62.5, "barWeight": 15, "plates": [ { "weight": 10, "count": 2 }, { "weight": 5, "count": 4 }, { "weight": 2.5, "count": 2 }, { "weight": 1.25, "count": 2 } ] } } } } } }, "responses": { "200": { "description": "Calculation result envelope.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/OneRepMaxCalculatorResult" } } } }, "400": { "description": "Malformed JSON body.", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "422": { "description": "Invalid input (see errors[]).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "429": { "description": "Rate limit exceeded (see Retry-After).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } } } } }, "/api/v1/tool": { "get": { "operationId": "getToolDefinition", "summary": "Inputs, output schema and examples for this tool", "responses": { "200": { "description": "Tool definition.", "content": { "application/json": { "schema": { "type": "object" } } } } } } } }, "components": { "schemas": { "Problem": { "type": "object", "description": "RFC 9457 problem details. 422 responses include per-field `errors`.", "required": [ "type", "title", "status", "detail" ], "properties": { "type": { "type": "string" }, "title": { "type": "string" }, "status": { "type": "integer" }, "detail": { "type": "string" }, "code": { "type": "string" }, "errors": { "type": "array", "items": { "type": "object", "required": [ "field", "message" ], "properties": { "field": { "type": "string" }, "message": { "type": "string" } } } } } }, "OneRepMaxCalculatorInput": { "type": "object", "additionalProperties": false, "properties": { "weight": { "title": "Weight lifted", "type": "number", "minimum": 0.5, "maximum": 2000, "default": 100 }, "reps": { "title": "Repetitions", "description": "Reps completed in the set. Estimates are most reliable up to about 10 reps.", "type": "integer", "minimum": 1, "maximum": 30, "default": 5 }, "unit": { "title": "Unit", "type": "string", "enum": [ "kg", "lb" ], "default": "kg" }, "rpe": { "title": "RPE of the set", "description": "Optional (6–10). 10 = to failure; 8 = two more reps were possible. Reps in reserve are added before estimating.", "type": "number", "minimum": 6, "maximum": 10 }, "targetWeight": { "title": "Weight to load", "description": "Optional total bar weight for the plate loader.", "type": "number", "minimum": 0, "maximum": 2000 }, "targetPercent": { "title": "Or: percentage of 1RM to load", "description": "Used when no weight to load is given; default 100% of the average estimate.", "type": "number", "minimum": 1, "maximum": 110, "x-unit": "%" }, "barWeight": { "title": "Bar weight", "description": "Default 20 kg or 45 lb.", "type": "number", "minimum": 0, "maximum": 100 }, "collarWeight": { "title": "Collars (both together)", "type": "number", "minimum": 0, "maximum": 20, "default": 0 }, "plates": { "title": "Plates available", "description": "Plate weight and how many you have in total (both sides). Empty = a standard set (kg: 25–1.25, lb: 45–2.5).", "type": "array", "maxItems": 15, "items": { "type": "object", "additionalProperties": false, "properties": { "weight": { "title": "Plate weight", "type": "number", "minimum": 0.05, "maximum": 100 }, "count": { "title": "Count", "type": "integer", "minimum": 0, "maximum": 100 } }, "required": [ "weight", "count" ] } } }, "required": [ "weight", "reps" ] }, "OneRepMaxCalculatorResult": { "type": "object", "additionalProperties": false, "required": [ "schemaVersion", "tool", "computedAt", "inputs", "summary", "result", "units", "assumptions", "sources", "warnings", "presentation", "links" ], "properties": { "schemaVersion": { "type": "string", "const": "1.0" }, "tool": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "version" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "version": { "type": "string" } } }, "computedAt": { "type": "string", "format": "date-time" }, "inputs": { "type": "object", "description": "Normalised inputs actually used, including applied defaults." }, "summary": { "type": "string" }, "result": { "type": "object", "additionalProperties": false, "required": [ "unit", "weight", "reps", "effectiveReps", "estimates", "average", "percentTable", "rpeTable", "loader" ], "properties": { "unit": { "type": "string", "enum": [ "kg", "lb" ] }, "weight": { "type": "number" }, "reps": { "type": "integer" }, "effectiveReps": { "type": "number", "description": "Reps + reps in reserve (10 − RPE)." }, "estimates": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "formula", "oneRepMax" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "formula": { "type": "string" }, "oneRepMax": { "type": "number" } } } }, "average": { "type": "number" }, "percentTable": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "percent", "weight", "approxReps" ], "properties": { "percent": { "type": "number" }, "weight": { "type": "number" }, "approxReps": { "type": [ "number", "null" ] } } } }, "rpeTable": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "reps", "rpe", "percent", "weight" ], "properties": { "reps": { "type": "integer" }, "rpe": { "type": "number" }, "percent": { "type": "number" }, "weight": { "type": "number" } } } }, "loader": { "type": "object", "additionalProperties": false, "required": [ "target", "bar", "collars", "exact", "perSide", "loaded", "method", "nearestBelow", "nearestAbove" ], "properties": { "target": { "type": "number" }, "bar": { "type": "number" }, "collars": { "type": "number" }, "exact": { "type": "boolean" }, "perSide": { "type": "array", "items": { "type": "number" } }, "loaded": { "type": [ "number", "null" ] }, "method": { "type": [ "string", "null" ] }, "nearestBelow": { "type": [ "object", "null" ], "additionalProperties": false, "properties": { "total": { "type": "number" }, "perSide": { "type": "array", "items": { "type": "number" } } } }, "nearestAbove": { "type": [ "object", "null" ], "additionalProperties": false, "properties": { "total": { "type": "number" }, "perSide": { "type": "array", "items": { "type": "number" } } } } } } } }, "units": { "type": "object", "additionalProperties": { "type": "string" } }, "assumptions": { "type": "array", "items": { "type": "string" } }, "sources": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "title" ], "properties": { "title": { "type": "string" }, "url": { "type": "string" }, "publisher": { "type": "string" }, "retrievedAt": { "type": "string" }, "note": { "type": "string" } } } }, "warnings": { "type": "array", "items": { "type": "string" } }, "presentation": { "type": "array", "items": { "type": "object" }, "description": "Display blocks used by the human page (same data)." }, "links": { "type": "object", "additionalProperties": false, "required": [ "human", "api", "openapi", "methodology" ], "properties": { "human": { "type": "string", "format": "uri" }, "api": { "type": "string", "format": "uri" }, "openapi": { "type": "string", "format": "uri" }, "methodology": { "type": "string", "format": "uri" } } } } } } } }