Simple Frame Time Calculator for Unity. Works with TextMeshPro. Sends to DebugLog if TMPro is unavailable.

FPSCounter.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace OccaSoftware
{
    public class FPSCounter : MonoBehaviour
    {

        float deltaTime;
        float realtimePrevious;
        float trailingAvg;

        float delayDuration = 3f;
        float timeSinceActive = 0f;

        bool startCheckingFrameData = false;

        TMPro.TextMeshProUGUI text;

        private void Start()
        {
            if (TryGetComponent(out TMPro.TextMeshProUGUI temp))
            {
                text = temp;
                text.SetText("");
            }
        }

        void Update()
        {
            if (!startCheckingFrameData)
            {
                DoWait();
            }
            else
            {
                DoCheckFrameData();
            }
        }


        void DoWait()
        {
            timeSinceActive += Time.deltaTime;
            if (timeSinceActive > delayDuration)
            {
                startCheckingFrameData = true;
                trailingAvg = Time.deltaTime / 0.001f;
                realtimePrevious = Time.realtimeSinceStartup;
            }

        }

        void DoCheckFrameData()
        {
            float delta = Time.realtimeSinceStartup - realtimePrevious;
            realtimePrevious = Time.realtimeSinceStartup;
            delta /= 0.001f;
            trailingAvg = Mathf.Lerp(trailingAvg, delta, 0.005f);

            string trailingAvgStr = string.Format("{0:N2}", System.Math.Round(trailingAvg, 2));
            string deltaStr = string.Format("{0:N2}", System.Math.Round(delta, 2));
            string trailingFpsStr = string.Format("{0:N0}", 1000.0f / trailingAvg);
            string textToPrint = "trailing avg (ms) " + trailingAvgStr + "\ncurrent frame (ms) " + deltaStr + "\nFPS " + trailingFpsStr;

            if (text == null)
                Debug.Log(textToPrint);
            else
                text.SetText(textToPrint);
        }
    }
}